We want to buy a small SIP based VoIP GSM gateway to serve 2 purposes.
1. If customer call, a call will be received on this GSM gateway and will be forwarded over VoIP to our IP PBX and our staff receive calls
2. If customer send SMS then we receive this SMS to our email
3. If we send SMS, we should be able to send the SMS out through this VoIP GSM gateway.
So in other words, we want SMS send/receive all working + outgoing and incoming calls all working on our GSM SIM. And each SIM gives us the local number and our staff able to make outbound calls if required and receive incoming calls on the number and send/receive SMS as well.
I know there are many such gateways available, however it's difficult for us to make a choice and I want someone to assist us who has done similar job in past already and you assist us in buying the right hardware and help us setup this for us.