The primary difference in Pay As You Go and Pick Your Plan is the way in which the GoPhone account is refilled:
Pay As You Go Customers
Refill their account as needed with refill cards or PIN's purchased at any one of 60,000 AT&T stores, authorized dealers, or retail locations.
Pick Your Plan Customers
Set up monthly automatic payments with a debit card, credit card, or checking account.
Still not sure where to go? Log in and you will be directed to the proper place to manage your GoPhone account.