I can definitely help you out with porting your phone number to AT&T! I love the name by the way, mj23, I’m from Chicago and I grew up on the Chicago Bulls!
To port in a phone number, you can do it any one of the three ways you mentioned – online, in store, or over the phone.
If you select to port the phone number from another carrier online, you will want to confirm that it is eligible by visiting the Transfer your Number to AT&T website. Don't cancel your current phone service with your other carrier! AT&T will take care of that for you when you activate your new service.
So, I looked on the page you linked to, with the step-by-step process, and the "contact us" link took me to a number that was also the 611 number, which is fully automated. Apparently there is no way to talk to a real person, so how exactly are you supposed to port in a number from another carrier? There's no way to do it on the website, since we don't have access to the full myATT website. I don't have access to chat, either. I'm kind of confused about how I'm supposed to get customer service??
Only in store. They don’t tell you that on the prepaid site or during sign up, take your money and give no info. And you have to ask for tech support to speak to a person, just say representative and then tech support then other. Dispute the charge if like me you can’t get to the store because they don’t care about this and their lying by omission. The CSR told me they have you compile all the info listed and call to be told to go to the store. Blatant facts. Why they don’t state that up front I don’t know. Probably get a lot of people on wasted service that way. You live far from a store or disabled, just too bad too sad they say. Take it up with who you used to pay! Services not rendered, some of us need our numbers.