Make sure your prepaid phone is AT&T compatible. It is better if you pick up a prepaid plan at the store. The Best Buy associates will even help you with the setup. After your first prepaid purchase, login to your AT&T Prepaid web site https://www.paygonline.com and from there you can your account on auto payment and see your data usage. You can also do one-time refills from the phone, the web site, or go to Best Buy and purchase another refill card. Hope this helps