Decombine landline, DSL, from wireless bill.

I am an AT&T active employee. I am at an AT&T mobility store trying to upgrade my cell phone. I have been told this is not possible because my account is combined. I have spent 4 hours on the phone with various departments trying to decombine my billing so I can get the new cell phone I want. No one has been able to help, and I keep getting passed from one department to another. Why is this so difficult to do??? Please help!!!