Lord Azrael said:
I'm trying to find out how do they work in AT&T, and what the conditions were. Sprint has pretty simple steps, but I've heard that for this carrier it's more complicated.

Very broad question. Send me a PM with a more focused question and I will be able to better answer you. As for the generic answer, on most smart phones, it is device based. Non-smart phones you can restrict calls on them. The text restriction is a feature code added in the billing systems (CARE, TELEgence, or NBI depending on your market and type of account)