I already have an AT&T account and pay monthly for U-Verse internet, but now I want to start using their wireless phone service. Do I "Add a Line" to my account or say that I'm new to AT&T? If I try adding a line, the website gives me an error message. I don't want to say I'm new to AT&T, because I've already been paying them for years. Am I just comprehending something wrong here?