Hi,
Its possible that something may not be provided from the switch side in this case. But it really depends on the protocol you are running in this case. What is being used here? Analog? Or GC with ISDN or PDK variant?
Need a little more detail about the actual setup in this case?
What specific information are you trying to extract out of g_getcallinfo as there are a couple parameters which can be used in that case as per the docs.
Regards,
Jeff