By using Portech SBK-32 expander for 32 SIM-cards, you can increase the number of channels in the Portech MV-37X GSM VoIP gateway series using the Internet.
international voip wholesales:
mobile dialer & reseller for a2z country, a2z route, also voipswitch +mobile dialer+pc2phone all mode: cheap rate, contac me: ranju@live.com.bd or sales@rimi-telecom.net