UPDATE! It's FIXED!!
Thank you for all of your help, I am happy to report my issues are now resolved! I wanted to post my solution here in case it helps someone else out! I should have just listened to the ATT people in the first place!
All I had to do was update my SIM card from the 64K which I had been using to a 3G SIM card! As soon as I got that new card in there, everything worked perfectly! I am getting ALL my calls, notifications of missed calls and text messages, and even better, my battery life has increase 10 fold!!!!!!!! It is amazing! Before my battery fully charged ALL NIGHT LONG, only lasted 4 hours MAX during the day, I was so ready just to chuck the phone! I had to have it plugged in all day and night or I was stuck without battery life! Now, with just the updated SIM card, my phone has been powered on for 10 hours already today and still has 4 out of the 5 bars left of juice! I am so excited! Iloved this phone and was sure I was going to have to give it up because of all of my issues! HOpefully my resolution helps someone out there!