Billing for the great multi-tenant IPBX Fusionpbx https://github.com/fusionpbx/fusionpbx
In /var/www/html/fusionpbx install the directory "mybilladmin" with all content, customise cfg.php and point your browser to the url
https://yourfusion_pbx, login as admin, then you can go to https://yourfusion_pbx/mybilladmin
start by importing rates. prepair a complete csv file using this format:
336;France-mobile-06;;0;0;200;1000
337;;France-mobile-07;;0;0;200;1000
331;;France-fixed-01;;0;0;200;1000
You can get a "csv" price list on many SIP Trunking Provider website to help you.
That's all you are ready to bill any account.
!! The scrip is auto-installable without any action and create the needed DB !!