It's just like how other's have posted here. It didn't take up full one hour. Studying the questions that's listed on the website helps a lot, but also asked couple of generic questions like why did you choose AT&T, and what do you know about the program. So make sure you're prepared for both the behavioral and questions like those.

Applied online and heard back a couple weeks later about taking a behavioral quiz. It was 88 questions long and was pretty simple. I was then had a skype interview which was pretty simple with mostly behavioral questions. Interviewer seemed kind of uninterested but was nice enough. I recieved an email saying I was no longer being considered around a week later.