This is a little different than my normal content but after much googling last night, I noticed that this information isn’t out there anywhere. At least not for this specific problem.

Here's the card and sticker with activation instructions. Notice it's only good for 3 months.
We (my husband and I) switched from Comcast to AT&T U-verse in December. There wasn’t a lot of thought put into it, just that Comcast had caused one too many problems that they refused to fix and/or give us answers to. AT&T’s service has actually been great so far and the installer was awesome.
About 2-3 weeks ago, I got a letter in the mail from AT&T saying that we were eligible for a $100 Visa gift card for purchasing the equipment that we got. I went to the website listed, entered the ID number on the letter and was given a confirmation that said I would have my card in 4-6 weeks. I got it in less than 3 weeks and couldn’t have been happier, until we tried to activate it.
The sticker on the card says to either call or go to their rewards center and enter the last 4 digits of the billing phone number on your account as the PIN to complete the activation. This is where we ran into all of the trouble. We went to the website first and tried the last 4 digits of my cell number, which is the billing phone number on our account. It was incorrect. Next we tried his number. Still incorrect. Finally, we tried our U-verse phone number. Nope, now we’re locked out. By now, we’re both annoyed since there is nothing helpful on the website or in the envelope that the card came in to direct us where to go next, so we call the 800 number. There are 2 options: report your card lost or stolen and activate your card. No option to speak to anyone. We tried activating it over the phone and after the third wrong entry it finally gave us an option to speak to someone. The phone rang a couple times and then another recording picked up saying that they are only open from 7am to 7pm CST. It was 5:30pm PST here. Quite honestly, I was mad at this point, more out of frustration that such a simple task was proving to be so difficult than I was at AT&T or their rewards center.
This morning, I called the 800 number again and was able to get through to a customer service rep by pressing the # key a few times whenever it asked for the card number. The first thing the rep said after I explained the situation was “Oh, your card is marked wrong. It’s supposed to be the last 4 digits of your account number.” She went on to say that there are cards for U-verse customers and cards for basic telephone customers. The U-verse cards are supposed to say to use your account number rather than your phone number and apparently mine had been mislabeled. Judging by her tone of voice and how quickly she was able to tell me what was wrong, this seems to be a fairly widespread issue. The rep was then able to activate the card in less time than it took me to get through the menu to speak to her and all is well now. I am, however, going to say this again:
If you got a rewards card for signing up with U-verse, try the last 4 digits of your ACCOUNT number instead of your phone number to activate your card. You only get 3 tries to do this before you are locked out of both the phone and website activation systems and have to have a representative activate it for you. Also, remember that the customer service center hours are 7am – 7pm CST, so that’s 5am – 5pm PST and the card is only good for 3 months after you receive it, so don’t wait until the last minute to activate in case you run in to trouble with the process.
I’m really not mad/annoyed/frustrated with AT&T or anyone else for that matter. I was able to get the issue resolved, it just would have been nice to be able to find some additional help on their website or be able to talk to someone a little later in the evening.