... change 3,support sending SMS & USSD 1/4/8/16 ports gsm voip gateway,wireless voip gateway VoIP ... 16)Model of GSM VoIP GatewayWe have 1, 4, 8, 16 ports GSM VoIP Gateway. there are 7 models. ... SIM cards, built-in antenna)GoIP-8( supporting 8 SIM cards ), GoIP-8i ( supporting 8 SIM cards, built-in antenna)model ... tech support untill your gateway runs. 1/4/8/16 ports gsm voip gateway,wireless voip gateway