diff --git a/LICENSE b/LICENSE
index 0d37b6c5..74911bc5 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2017-2023 Xendit
+Copyright (c) 2017-2024 Xendit
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/README.md b/README.md
index c719f128..6ef9f670 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@
 The official Xendit Go SDK provides a simple and convenient way to call Xendit's REST API
 in applications written in Go.
 
-* Package version: 4.1.0
+* Package version: 4.2.0
 
 # Getting Started
 
diff --git a/client.go b/client.go
index f8044064..eb6fb22f 100644
--- a/client.go
+++ b/client.go
@@ -154,7 +154,7 @@ func (c *APIClient) PrepareRequest(
 	headerParams["xendit-lib"] = "go"
 
 	// TODO: overwrite this line from buddy pipeline
-	headerParams["xendit-lib-ver"] = "4.1.0"
+	headerParams["xendit-lib-ver"] = "4.2.0"
 
 	var body *bytes.Buffer
 
diff --git a/configuration.go b/configuration.go
index d0238dc8..7a59e50e 100644
--- a/configuration.go
+++ b/configuration.go
@@ -78,7 +78,7 @@ var Default Configuration = *NewConfiguration()
 func NewConfiguration() *Configuration {
 	cfg := &Configuration{
 		DefaultHeader:    make(map[string]string),
-		UserAgent:        "OpenAPI-Generator/4.1.0/go",
+		UserAgent:        "OpenAPI-Generator/4.2.0/go",
 		Debug:            false,
 		Servers:          ServerConfigurations{
 			{
diff --git a/docs/InvoiceApi.md b/docs/InvoiceApi.md
index 4982bf6e..30d26ee2 100644
--- a/docs/InvoiceApi.md
+++ b/docs/InvoiceApi.md
@@ -356,7 +356,7 @@ Model Documentation: [InvoiceCallback](invoice/InvoiceCallback.md)
 #### Usage Example
 Note that the example is meant to illustrate the contents of the callback object -- you will not need to instantiate these objects in practice
 ```go
-InvoiceCallbackJson := map[string]interface{}{
+InvoiceCallbackJson := `{
   "id" : "593f4ed1c3d3bb7f39733d83",
   "external_id" : "testing-invoice",
   "user_id" : "5848fdf860053555135587e7",
@@ -373,8 +373,7 @@ InvoiceCallbackJson := map[string]interface{}{
   "currency" : "IDR",
   "payment_channel" : "ALFAMART",
   "payment_destination" : "TEST815"
-}
-jsonData, _ := json.Marshal(InvoiceCallbackJson)
+}`
 ```
 
 You may then use the callback object in your webhook or callback handler like so,
@@ -395,7 +394,7 @@ func main() {
 
     // unmarshal callback object jsonData
     var InvoiceCallback invoice.InvoiceCallback
-    err := json.Unmarshal(jsonData, &InvoiceCallback)
+    err := json.Unmarshal([]byte(InvoiceCallbackJson), &InvoiceCallback)
     if err == nil {
         fmt.Fprintf(os.Stdout, "Callback Object ID: %v\n", InvoiceCallback.GetId())
         // do things here with the callback
diff --git a/docs/PaymentMethodApi.md b/docs/PaymentMethodApi.md
index 74391400..3f0b320b 100644
--- a/docs/PaymentMethodApi.md
+++ b/docs/PaymentMethodApi.md
@@ -672,7 +672,7 @@ Model Documentation: [PaymentMethodCallback](payment_method/PaymentMethodCallbac
 #### Usage Example
 Note that the example is meant to illustrate the contents of the callback object -- you will not need to instantiate these objects in practice
 ```go
-PaymentMethodCallbackJson := map[string]interface{}{
+PaymentMethodCallbackJson := `{
   "event" : "payment_method.activated",
   "data" : {
     "id" : "pm-6ff0b6f2-f5de-457f-b08f-bc98fbae485a",
@@ -710,8 +710,7 @@ PaymentMethodCallbackJson := map[string]interface{}{
   },
   "created" : "2022-08-12T13:30:59.074277334Z",
   "business_id" : "5f27a14a9bf05c73dd040bc8"
-}
-jsonData, _ := json.Marshal(PaymentMethodCallbackJson)
+}`
 ```
 
 You may then use the callback object in your webhook or callback handler like so,
@@ -732,7 +731,7 @@ func main() {
 
     // unmarshal callback object jsonData
     var PaymentMethodCallback payment_method.PaymentMethodCallback
-    err := json.Unmarshal(jsonData, &PaymentMethodCallback)
+    err := json.Unmarshal([]byte(PaymentMethodCallbackJson), &PaymentMethodCallback)
     if err == nil {
         fmt.Fprintf(os.Stdout, "Callback Object ID: %v\n", PaymentMethodCallback.GetId())
         // do things here with the callback
diff --git a/docs/PaymentRequestApi.md b/docs/PaymentRequestApi.md
index 2b92fa38..81b83203 100644
--- a/docs/PaymentRequestApi.md
+++ b/docs/PaymentRequestApi.md
@@ -548,7 +548,7 @@ Model Documentation: [PaymentCallback](payment_request/PaymentCallback.md)
 #### Usage Example
 Note that the example is meant to illustrate the contents of the callback object -- you will not need to instantiate these objects in practice
 ```go
-PaymentCallbackJson := map[string]interface{}{
+PaymentCallbackJson := `{
   "event" : "payment.succeeded",
   "data" : {
     "id" : "ddpy-3cd658ae-25b9-4659-aa36-596ae41a809f",
@@ -604,8 +604,7 @@ PaymentCallbackJson := map[string]interface{}{
   "created" : "2022-08-12T13:30:58.986Z",
   "business_id" : "5f27a14a9bf05c73dd040bc8",
   "api_version" : null
-}
-jsonData, _ := json.Marshal(PaymentCallbackJson)
+}`
 ```
 
 You may then use the callback object in your webhook or callback handler like so,
@@ -626,7 +625,7 @@ func main() {
 
     // unmarshal callback object jsonData
     var PaymentCallback payment_request.PaymentCallback
-    err := json.Unmarshal(jsonData, &PaymentCallback)
+    err := json.Unmarshal([]byte(PaymentCallbackJson), &PaymentCallback)
     if err == nil {
         fmt.Fprintf(os.Stdout, "Callback Object ID: %v\n", PaymentCallback.GetId())
         // do things here with the callback
diff --git a/docs/RefundApi.md b/docs/RefundApi.md
index d73a26f3..6e65d214 100644
--- a/docs/RefundApi.md
+++ b/docs/RefundApi.md
@@ -333,7 +333,7 @@ Model Documentation: [RefundCallback](refund/RefundCallback.md)
 #### Usage Example
 Note that the example is meant to illustrate the contents of the callback object -- you will not need to instantiate these objects in practice
 ```go
-RefundCallbackJson := map[string]interface{}{
+RefundCallbackJson := `{
   "event" : "refund.succeeded",
   "business_id" : "5f27a14a9bf05c73dd040bc8",
   "created" : "2020-08-29T09:12:33.001Z",
@@ -354,8 +354,7 @@ RefundCallbackJson := map[string]interface{}{
     "updated" : "2020-08-30T09:12:33.001Z",
     "metadata" : null
   }
-}
-jsonData, _ := json.Marshal(RefundCallbackJson)
+}`
 ```
 
 You may then use the callback object in your webhook or callback handler like so,
@@ -376,7 +375,7 @@ func main() {
 
     // unmarshal callback object jsonData
     var RefundCallback refund.RefundCallback
-    err := json.Unmarshal(jsonData, &RefundCallback)
+    err := json.Unmarshal([]byte(RefundCallbackJson), &RefundCallback)
     if err == nil {
         fmt.Fprintf(os.Stdout, "Callback Object ID: %v\n", RefundCallback.GetId())
         // do things here with the callback
diff --git a/docs/refund/RefundCallbackData.md b/docs/refund/RefundCallbackData.md
index 63a805f4..8fedafb4 100644
--- a/docs/refund/RefundCallbackData.md
+++ b/docs/refund/RefundCallbackData.md
@@ -5,7 +5,7 @@
 | Name | Type | Required | Description | Examples |
 |------------|:-------------:|:-------------:|-------------|:-------------:|
 | **Id** | **string** | ☑️ |  |  |
-| **PaymentRequestId** | **string** | ☑️ |  |  |
+| **PaymentId** | **string** | ☑️ |  |  |
 | **InvoiceId** | Pointer to **NullableString** |  |  |  |
 | **PaymentMethodType** | **string** | ☑️ |  |  |
 | **Amount** | **float64** | ☑️ |  |  |
@@ -25,7 +25,7 @@
 
 ### NewRefundCallbackData
 
-`func NewRefundCallbackData(id string, paymentRequestId string, paymentMethodType string, amount float64, channelCode string, status string, reason string, country string, currency string, created string, updated string, ) *RefundCallbackData`
+`func NewRefundCallbackData(id string, paymentId string, paymentMethodType string, amount float64, channelCode string, status string, reason string, country string, currency string, created string, updated string, ) *RefundCallbackData`
 
 NewRefundCallbackData instantiates a new RefundCallbackData object
 This constructor will assign default values to properties that have it defined,
@@ -60,24 +60,24 @@ and a boolean to check if the value has been set.
 SetId sets Id field to given value.
 
 
-### GetPaymentRequestId
+### GetPaymentId
 
-`func (o *RefundCallbackData) GetPaymentRequestId() string`
+`func (o *RefundCallbackData) GetPaymentId() string`
 
-GetPaymentRequestId returns the PaymentRequestId field if non-nil, zero value otherwise.
+GetPaymentId returns the PaymentId field if non-nil, zero value otherwise.
 
-### GetPaymentRequestIdOk
+### GetPaymentIdOk
 
-`func (o *RefundCallbackData) GetPaymentRequestIdOk() (*string, bool)`
+`func (o *RefundCallbackData) GetPaymentIdOk() (*string, bool)`
 
-GetPaymentRequestIdOk returns a tuple with the PaymentRequestId field if it's non-nil, zero value otherwise
+GetPaymentIdOk returns a tuple with the PaymentId field if it's non-nil, zero value otherwise
 and a boolean to check if the value has been set.
 
-### SetPaymentRequestId
+### SetPaymentId
 
-`func (o *RefundCallbackData) SetPaymentRequestId(v string)`
+`func (o *RefundCallbackData) SetPaymentId(v string)`
 
-SetPaymentRequestId sets PaymentRequestId field to given value.
+SetPaymentId sets PaymentId field to given value.
 
 
 ### GetInvoiceId
diff --git a/refund/model_refund_callback_data.go b/refund/model_refund_callback_data.go
index fd2b6bb7..2efe2853 100644
--- a/refund/model_refund_callback_data.go
+++ b/refund/model_refund_callback_data.go
@@ -21,7 +21,7 @@ var _ utils.MappedNullable = &RefundCallbackData{}
 // RefundCallbackData struct for RefundCallbackData
 type RefundCallbackData struct {
 	Id string `json:"id"`
-	PaymentRequestId string `json:"payment_request_id"`
+	PaymentId string `json:"payment_id"`
 	InvoiceId NullableString `json:"invoice_id,omitempty"`
 	PaymentMethodType string `json:"payment_method_type"`
 	Amount float64 `json:"amount"`
@@ -42,10 +42,10 @@ type RefundCallbackData struct {
 // This constructor will assign default values to properties that have it defined,
 // and makes sure properties required by API are set, but the set of arguments
 // will change when the set of required properties is changed
-func NewRefundCallbackData(id string, paymentRequestId string, paymentMethodType string, amount float64, channelCode string, status string, reason string, country string, currency string, created string, updated string) *RefundCallbackData {
+func NewRefundCallbackData(id string, paymentId string, paymentMethodType string, amount float64, channelCode string, status string, reason string, country string, currency string, created string, updated string) *RefundCallbackData {
 	this := RefundCallbackData{}
 	this.Id = id
-	this.PaymentRequestId = paymentRequestId
+	this.PaymentId = paymentId
 	this.PaymentMethodType = paymentMethodType
 	this.Amount = amount
 	this.ChannelCode = channelCode
@@ -90,28 +90,28 @@ func (o *RefundCallbackData) SetId(v string) {
 	o.Id = v
 }
 
-// GetPaymentRequestId returns the PaymentRequestId field value
-func (o *RefundCallbackData) GetPaymentRequestId() string {
+// GetPaymentId returns the PaymentId field value
+func (o *RefundCallbackData) GetPaymentId() string {
 	if o == nil {
 		var ret string
 		return ret
 	}
 
-	return o.PaymentRequestId
+	return o.PaymentId
 }
 
-// GetPaymentRequestIdOk returns a tuple with the PaymentRequestId field value
+// GetPaymentIdOk returns a tuple with the PaymentId field value
 // and a boolean to check if the value has been set.
-func (o *RefundCallbackData) GetPaymentRequestIdOk() (*string, bool) {
+func (o *RefundCallbackData) GetPaymentIdOk() (*string, bool) {
 	if o == nil {
 		return nil, false
 	}
-	return &o.PaymentRequestId, true
+	return &o.PaymentId, true
 }
 
-// SetPaymentRequestId sets field value
-func (o *RefundCallbackData) SetPaymentRequestId(v string) {
-	o.PaymentRequestId = v
+// SetPaymentId sets field value
+func (o *RefundCallbackData) SetPaymentId(v string) {
+	o.PaymentId = v
 }
 
 // GetInvoiceId returns the InvoiceId field value if set, zero value otherwise (both if not set or set to explicit null).
@@ -542,7 +542,7 @@ func (o RefundCallbackData) MarshalJSON() ([]byte, error) {
 func (o RefundCallbackData) ToMap() (map[string]interface{}, error) {
 	toSerialize := map[string]interface{}{}
 	toSerialize["id"] = o.Id
-	toSerialize["payment_request_id"] = o.PaymentRequestId
+	toSerialize["payment_id"] = o.PaymentId
 	if o.InvoiceId.IsSet() {
 		toSerialize["invoice_id"] = o.InvoiceId.Get()
     }