T-Mobile to AT&T with fatcow Microsoft Exchange Help

Trying to help the wife setup her blackberry curve 8320

We have
T-Mobile phone that has been unlocked
Service setup with AT&T including BES
domain setup with fatcow which includes Microsoft Exchange and blackberry mobile services.

Looks like the email is working with Outlook just fine but i cannot get the phone to connect to the server.
Fatcow has connected to the account with one of thier Blackberries so they are saying we need to check with our provider.
AT&T says that BES is setup for the phone.

Would the fact that we has an un-locked T-Mobile phone be the issue?
I've updated to Desktop Manager 4.7, running 4.5.0.81 on her phone.

There is a field on the 8320 setup that ask for activation server address which i'm not sure what to put it. I've left it blank, put in the fatcow exchange server and all i get is failures to connect.

a couple time i've seen my PIN show up on the fatcow server statistics page but that is it.

Of course when i use my iphone to connect to her exchange service i was talking to it in 5 minutes but she is a die hard crackberry :-)

Any help would be appreciated.

thanks