Can i use an unlocked Blackberry 7100 - 8100 with Pay&talk (prepaid)?

[LaeStarcraft]

i was wondering if i get a blackberry that is unlocked, and i choose one of the carriers , since it has no contract and all can i just use it as a normal pay and talk service, i obviously know i wont get the unlimited web browsing features and all but just wondering if i could use it for prepaid purposes.