How to set up a GSM shield

I am going to buy a GSM shield, and it of course is not connected to anything without a SIM card, I have my cellular service through AT&T, so I want to buy a SIM card which will come up on the AT&T system. I don't want a contract, just a fixed-minutes arrangement, where I can pay an additional amount for more minutes when I need them. I know you can buy prepaid phones that work like that, so I would expect I can set the same thing up for a SIM card going into a GSM shield.

So my questions are:

  1. can I purchase a prepaid SIM card, based on prepaid minutes?

  2. do I then contact AT&T to set up a number for it?

Probably simple, but I haven't come across any discussions of this when googling.

Thanks in advance for any advice.

John Doner

Wouldn't you be better served asking AT&T these questions?