Phone not all its cracked up to be.......

Well if the phone is less than 1 year old, you cancertainly try to exchange it via Warranty Exchange or XBM. If you have had it for 30 or more days, then you are certaily free to purchase another device that may suit your needs. If it less than 30 days then you can send it back and get another phone I think. I am not so sure on the 30 days policy with Cingular now.

If you don't get voicemail immediately (or within a couple of minutes at the most) after you get back into GSM coverage you should contact your operator.
If your phone is freezing up it could be a firmware issue with the phone, once again contact your service provider.