LG Fathom on AT&T network

[acapde]

Yes, before buying the phone I checked the bands (supported by the phone and used by AT&T) and everything looked fine. However when I try to use the phone, if I use GSM/UMTS the phone always pick GSM (EDGE), if I tried to force ot to UMTS only then the phone just doesn't connect at all. I know I have UMTS in my area because if I put the same SIM in my BB Torch then it picks the 3G signal right away (and with good signal strength)...