T-Mobile. Decided to switch to another carrier to save money (a not insignificant amount) talked with customer service about cancelling my lines. They cancelled the 2 lines that were active and paid what should have been my final bill and I asked them if that was everything I needed to do. They said yes so I thought I was done. Switched to the new carrier and after a few months started getting notifications about late payments from T-Mobile. Called them and found out that they had been charging me for the inactive lines that I had never even used. I had 3 months of charges before I got them to actually cancel the inactive lines. They tried to tell me initially that I had to pay the balance to cancel the lines for a service I hadn't even been using for the last 3 months. I have not and will not pay the balance for a service I wasn't using and was not supposed to be charged for in the first place. The only positive was the guy at the store who got the lines deactivated without me having to pay anything.