I am wanting to change from AT&T to T-Mobile. I have an AT&T Blackberry 8820 v4.5.0.182 (Platform 2.7.0.106) that I recently unlocked. A friend of mine who is a T-Mobile customer has let me borrow his SIM card just long enough to to prove to us that my phone is unlocked. We can make and receive phone calls and access the internet using his card in my phone. However, he is able to get 3/4 EDGE signal and when we put the card in my phone I get 3/4 signal but only GSM. We are doing this test within minutes of each other and standing in the same location. We are traveling on a business trip now and in a rural area in Virginia. Some areas he get good signal, mainly along the interstate highway. However when we travel to our work about 15 miles off the interstate, he has no service. As most of you T-Mobile folks know, he gets VoIP when connected to a WiFi network and can make and receive calls without any problems. We have also tested the WiFi connection using my phone while his card is installed and I cannot make VoIP calls. I know I'm connected to the web as I can access sites with and without any SIM card. But when using his SIM card nothing we have tried lets me make VoIP calls. I would appreciate any help I can get. Depending on what I can make work I would like to change over to T-Mobile next week and tell AT&T good-bye forever.

Are you sure that's what you have?

I don't think AT&T ever had the 8830.
BlackBerry - 8800 - Specifications

Geeez, my bad, sorry 8820

just get the service book from t-mobile and download it to your phone

If you only get GSM with your SIM, then that means you don't have the correct BlackBerry data plan provisioned on your account. With a BlackBerry data plan, you'll get EDGE, or at least GPRS.

You'll never be able to make VoIP calls with that device on T-Mobile. To use UMA, you need a T-Mobile branded device.