Hi Asterisker, I noticed your profile and would like to offer you my project. We can discuss any details over chat. In fact we want to customize LinPhone ([url removed, login to view]) in order to have 3 things:
1. Keep current features of Linphone
2. Customize User Interface so that users can see Call Bundles offer, purchase a bundle and user for calls
3. Create a Backend Admin Panel from where we can create call bundles with prices, check download, usage and call statistics per user, daily, weekly, monthly, etc. Manage users, receive their complaints and assist them. If that is a work you can handle, please ping me.