Interface with GSM modem for sending AT, USSD and SMS commands

What I need to build: I need a server capable of sending commands to 3 GSM modems (3 Separate Thai Networks). These commands will send top up credit to a customer's mobile phone. You should be a programmer familiar with AT commands, GSM modems, USSD codes. I know this software exists as I currently use it with another provider. I need also need a management interface where I can: - Send Credit - View Confirmations - View Errors - Track balance - Send Recall commands - History of all records - API access / website communication GSM modem reference guide: [login to view URL]