... support imei change 3,support sending SMS & USSD 1/4/8/16 ports gsm voip gateway,wireless voip ... Gateway (GoIP-16)Model of GSM VoIP GatewayWe have 1, 4, 8, 16 ports GSM VoIP Gateway. there ... 1SIM card, built-in antenna)GoIP-4( supporting 4 SIM cards ), GoIP-4i ( supporting 4 SIM cards, built-in antenna) ... full tech support untill your gateway runs. 1/4/8/16 ports gsm voip gateway,wireless voip gateway ...