Canceling prepaid then coming back?

All that kind of depends on how you canceled. If you just stop paying for 59 days all you have to do is refill and restart your service with the same phone number. Same account, same everything.

If you just stop paying and don't pay for 60 days or more, your account is closed, number is lost and you have to buy a new SIM card and start all over again with a new phone number

But if you port your phone number out, you come back to AT&t. Essentially, as a brand new customer, you have to buy a new SIM card, select a new plan, or at least from one of the existing plans

Thank you very much for your reply!