SMS Callback API for Asterisk with a2billing

Description -SMS API integrate with A2billing mysql - PBX in a Flash I need an interface to allow the following on an Asterix PBX in a Flash system with A2Billing 1. User should be able to use their mobile phone and get the following functionality using ONLY text messaging i.e. SMS CallBack facilities: A solution that allows a User to text their telephone number to our server's DID so they can then be called back for a voice call - the solution should check the A2B database and match the sent telephone number to an existing account before a return call is made 2. User should be able to use the internet and get the following functionality using only their web browser i.e. Click to CallBack facilities: A solution that allows a User to enter their telephone number at our server's webpage so they can then be called back for a voice call - the solution should check the A2B database and match the sent telephone number to an existing account before a return call is made Callback (via dial in with generic CID in A2B) and a2billing etc. is already set up and working. You will need to be able to build the API and configuration it into A2Billing Callback. This project is about asterisk + A2billing server - Successful completion of this project will lead to more work