I have successfully set up 3CX Phone System IP PBX on my local network, and it is working perfectly. Now I need to provide my extensions/clients/softphones with real world telephone communication. I have an USB 3G GSM Voice Modem (Huawei E303) which is working perfectly as well, both with Data and Voice services (tested by the software came with it). I need your advice on how do I integrate this GSM Voice capable hardware (modem) with the existing 3CX Phone System. The official guide from 3CX says I need a VoIP Gateway to achieve this. I believe they meant some software which will bridge the hardware mechanism with the SIP end. What could be that software? I am using Microsoft Windows 7 Ultimate x64 and I would prefer a freeware interface. Thanks in advance.