I tried to pay using 1 card, it said failed, to use another card, which I did, and it succeeded. Then the first one succeeded.

Now I show an account credit for the full bill amount. Called to get the overpayment refunded, but how many days will that likely take. Why would the system say the first payment failed just to later succeed, but not till after I charged the second card. I hat ATT billing and payment system. Most places it is simple to cancel a transaction within an hour.