How to avoid being charged for data plan?

My brother put his old SIM into both a Blackberry and an iPhone and our family got charged for data plan. I don't know why that happened.

I want a phone but it requires data plan, which I don't want and don't want to pay for. If I buy it online without a contract, GSM, unlocked and is with Att (my current carrier) and put my old SIM in it, will it work (as in make phone calls and text) but not charge me data plan (because it is without a contract)?

Or does the whole 2-year contract and required data plan go hand in hand, and there's no avoiding it.

Any att smartphone requires a data plan.
att will add one as soon as the detect your using a smartphone.
use simple mobile or straight talk