Ask those cellular providers what the next step is. Sometimes you find them deny you access to their network in some way.
I was looking at the specifications on c-net Reviews for Samsung Galaxy S II, The part I need to understand Technology WCDMA (UMTS) / GSM Band WCDMA (UMTS) / GSM 850/900/1800/1900
The WCDMA part on the specifications since the phone is Unlocked can you use it for Verizon or Sprint or other CDMA providers If I understood that if the phone can go both ways??