I am looking for the kind of VOIP service, which can give me the room to test and enhance couple of the project.
The service must be the free inbound call, and the client side is open source based (such as SIP, IAX protocol support), it should give me the flexibility to make my own version of the client, otherwise, it will not be what I am looking for.
Please share me with your experience, and kindly give me some suggestions.
Thanks.


Dragondad