Can you do a cross upgrade using at&t's next program?
I have two lines, (A) and (B), Line (A) is an iPhone 5 updated last year. Line (B) is a flip phone hasn't been upgraded in years, so no contract consequently. I wanted to enroll for AT&T's next program and get an iPhone 5s at launch, but use line (B)'s upgrade and perform a cross upgrade. Is this possible? what are special conditions that I should be aware of by doing this?