We have signed up for SIP service with PLDT in the Philippines for our remote office. They brought in what appears to be a Cisco SBC Gateway and configured it with our server address as the signaling IP. What I'd like to know is how to configure 3CX to receive and make calls using this gateway? Is this even possible? I attempted to use the IP address and gateway they gave us and configured it as a Generic SIP without credentials, but I've had no success. Have I missed something obvious? Is it conceptually impossible?