I use Google Voice for all outgoing calls. When making a call, I sometimes get a single ring followed by a recorded message telling me that the feature I'm trying to use is not recognized or is unavailable. When this happens, repeated call attempts result in the same message. If I attempt the same call without Google Voice the call his right through. Guessing that this issue has something to do with the number that Google Voice is routing the call through, I've looked up the area codes used and they are always US numbers. So I don't think this should be a problem. Has anyone encountered this problem, or know what to do about it?