As you all know , Att requires you add a data plan when you purchase a discounted price smart phones (etc iPhone) from them. You are also required to make a 2 year contract.

But , when you bring your own device , you don't have to make a contract, and you can get a plan, use it and leave anytime you want w/o paying any penalty.

Here is what I wonder;

1 You might be out of their contract or;
2 You might have purchased an unlocked device by paying the full price or;
3 You might have brought your device from another provider or from another country which of course does not have any relation to Att

So in those cases , are you still required to add a plan when you get a month to month plan from Att?

Because normally (within a contract period) when you put your sim card in a smart phone it automatically adds the data plan. Is it same for those situations I described?

Yes, this is a common misconception. You are always under a contract with carriers. When you are outside of a contract term, you are said to be on a month-to-month basis under the contract. All other contract terms remain in place, including the requirement to have a data plan.

Yes, this is a common misconception. You are always under a contract with carriers. When you are outside of a contract term, you are said to be on a month-to-month basis under the contract. All other contract terms remain in place, including the requirement to have a data plan.
I think ATT will let you pay $5/mo to waive the data plan.

Its ridiculous. if they catch you with ANY smartphone they add a data plant to it...usually only AT&T locked phones even if you bought it from someone other than AT&T