The current firmware in the Digium G series gateways have a quirk that if they don’t receive caller ID name they move the caller Id number to be the Caller Id name but don’t leave the Caller Id number in place. The relies on you setting “trustrpid=yes” in teh sip trunk configuration.
We have produced a short document on settings for using the gateway with any freePBX based asterisk solution. It can be downloaded here