No, we are not a GSM provider. But we can handle calls to GSM and PSTM numbers and receive inbound calls, if you are using a SIP provider with GSM/PSTN call termination capabilities or if you have a hardware SIP-GSM gateway or a hardware card with sockets for SIM cards and PBX server supporting such hardware.
Flashphoner will communicate with such GSM equipment via SIP and RTP, therefore a GSM call can be established.