The remote party has ended this connection

[Guest otech]

So I unlocked my HTC Juno/T-mobile Shadow cause I switched to AT&T with a Samsung Flight. Everything went smoothly except I have 3G support with AT&T and when I try to go online with the HTC when not connected to a wireless network, I get the same Error: The remote party has ended this connection.

Not sure if this has something to do with AT&T or simply because the HTC only supports EDGE, not 3G. Does anyone know if i have to talk to AT&T about configuring the data plan or something? Thanks.