Very weird problems. When calls come in to our phone system from callers on the AT&T wireless network there are issues with the auto attendant menus and with missing ring tone when the calls are trying to connect. If an AT&T caller calls our main number, gets the auto attendant menu, and then attempts to access our voicemail service at extension 125, the system does not recognize the input and immediately starts playing the auto attendant prompt again. We can access our regular extensions in the 700 range without a problem from the auto attendant prompt, just not our voicemail. AT&T callers calling in to our system do not hear a ring tone when waiting for dialed extension to pickup. The caller hears silence until the call is answered or the call is routed to voicemail. This occurs when accessing the extension from the main menu or when direct dialing in to an extension DID. An unanswered call does finally ring one time as the system routes the call to voicemail but this is after 20 seconds of silence. We have been able to consistently reproduce both issues. We never have a problem when users are calling in from a land line. We have also been successful calling in from phones on the Verizon and Sprint wireless networks. The only time we have these failures is when the call comes from AT&T wireless. Is there some sort of tone generation incompatibility between 3CX and AT&T?