Should be ok Bro, Some of the local AP unit is a AT&T set. Mine is T-Mobile work like a charm.
The only operator known having compatibility issue with Celcom so far is CDMA unit from Verizon.

By the way i am new Onyx user, upgrade from Bold 9000. So far the extra RAM on board make a lot of difference.
The theme from 8900 and bold 9000 are still usable in Bold 2.