I can't speak to how CDMA operators (Verizon, Sprint etc.) work, but in all GSM systems to my knowledge if you are roaming and a call comes in if you do not answer it you will have a minimum of two charges one for the call finding you in the remote location and another charge for going back to your origin to roll the call to voicemail.

As for charging it depends on what you've programmed on your phone. If you've programmed unconditional forward to voicemaii (**21*[voicemail center no.]#) everything will go directly to voicemail. Also consider that if you have operated your phone in a roaming area it will remain in that area and you will be charged for a roaming call. If you have not used the phone past midnight when the days roaming is renewed you will have no "foreign" calls charged and all calls will go to voicemail. If you use conditional forwards (codes 61, 62 or 67) you will be charged regular roaming rate.

This somewhat geeky but applies to all GSM operators (in the US that's mainly AT&T and T-Mobile):

http://wiki.howardforums.com/index.p..._Network_Codes