PSA: AT&T apparently can't move phone numbers from an AT&T reseller/MVNO to an AT&T prepaid account
I see some other questions from people trying to do something similar, and there seem to be some question about whether or not it's possible. This will recount my experience. This is how AT&T took ~$35 of my money and a few hours of my time and gave me nothing in return.
When this all started, I was an Airvoice Wireless prepaid customer. Airvoice is an AT&T reseller/MVNO.
9/28: Ordered a new AT&T prepaid SIM card from AT&T's online store. The automated process told me my number couldn't be ported, but the "can I port my number?" page on AT&T's site said it should be fine. I started a web support chat to get clarification and was told to go ahead and order the SIM with a new number, and I'd be able to port my number after the fact.
10/1: Received and activated my new SIM card. Called the prepaid support line and asked about bringing my number over. Was told that it looked like my number was associated with a postpaid account (?), and there wasn't anything he'd be able to do about it. I'd have to go to an AT&T Corporate Store and ask for a number "migration". I was confused, as my number is currently on an prepaid account, but I didn't want to quiz him too much as I was having a hard time understanding him anyway.
10/7 am: Went to AT&T Corporate Store and recounted the above. Was told by the rep that I talked to that my number was attached to a corporate account (??), and she couldn't do anything about it until I addressed that with the company that held the account. But she couldn't tell me what company held the account. I checked with the guy who runs my employer's corporate cell phones (even though my number has never been associated with the company account), and he verified that no, my number is not on the company account.
10/7 noonish: Called the AT&T porting department and explained the situation. The person I talked to here seemed to be able to actually identify the line as belonging to an AT&T reseller. He told me that I needed to go back to the Corporate Store with my account number and PIN from the reseller, and they'd have to move the number to a new AT&T prepaid SIM card and move the balance over to that from my first AT&T SIM card.
10/7 pm: Went back to the Corporate Store (10 miles away, so this is a total of 40 miles/80 minutes of driving today) and explained this all to a different rep. He just gave me a deer in headlights look and asked someone else to help. I went over it again, and after five minutes of hemming and hawing and looking things up on their tablets, they finally told me that they simply can't move a number from an AT&T reseller to an AT&T prepaid account. And since it was a prepaid account, I couldn't get any of my money back that I put into the first card, even though there were no calls/texts in/out and the SIM card had only been in the phone long enough to activate it in the first place.
Needless to say, I'm extremely unhappy with this experience and have lost all desire to become an AT&T customer. I'll be staying with Airvoice now.