This might seem a bit silly. But I tried to find a customer support phone number on the AT&T Site. In the end, I had to Google it.
Here is the page:
AT&T Wireless Customer Support Page
And the number:
Customer Service 1-800-331-0500
Update: On another humorous note, my first attempt to look up the number was on my iPhone. I discovered AT&T does not yet have a mobile version of their site. Of course neither does Apple. lol.