Asterisk+A2Billing+openser+mysql

We looking for expert in Openser+asterisk+A2billing to build for us the complete Virtual calling card Platform with Web User Interface that will be displayed to our customers who will buy or refill calling card online. The Callback/Simultaneous call negative balance shall resolved a so that user account does not reach the Negative balance. Openser+ asterisk shall be configured in REaltime Usin MySQL DB. There will be initially 2- Server provided for this project on Public IP. Eventually other server will be add as the calls volume grows. The programmer will provide full documentation and comment the code and also the stepby step guide guide. Please attached file for the requirement and if any further details will be provided. The pmt will be 50% Day b4 Delivery of site and installation, 50% 15 days after the delivery. All payment will be in GAF escrow. The Delivery time and schedule should strickly adhered. We do speak other languages, but programmer shall be able to communicate in english. We will appreciate if u provide links to the site either you have done in past related to this project or PM the links that you think u will immplement for this project. We are running a softswitch already in our Setup we will provide the details of the switch via pm if needed. This switch will do wholesale or if Needed Callback for us. you must be to provide interconnection for the module. -We Are looking for SIP to SIp -Sip To PSTN -DID Resale using Didx or Voxbone. -G729, G723, G711 Support Please feel free to send email with yr queries or any explantion u need regarding this project. Abid The programmer shall give tel/Online support for 3-months.