AT&T may have the worst customer service and/or customer support I’ve ever had to deal with. On December 31st my phone screen went completely black. I was told it would take 4-5 days to be able to fix my phone and I couldn’t be without a phone for even one day. My only option after being at an AT&T store for hours was to buy a new phone and get service on that phone until I could get my phone fixed.I was told that as long as I returned that new phone within 30 days I could get a full refund. So, I got my original phone fixed and then returned the new phone I bought. The person I dealt with at the AT&T store had a very hard time getting my old phone service back on, but we eventually did. I was told service would be cancelled on the phone I was returning and went on my way. Tonight, while browsing through myAT&T, I notice that I’m “eligible for an upgrade” on my “paid off” iPhone 15 (the phone I returned). I thought that was odd. I went to check, and it looks like we are still paying for a service on a phone I have not had for 3 months now.Chatting with a “customer support specialist” I’m told that even though the phone was returned, I was supposed to call AT&T and tell them to cancel service on a line that had NO phone or device attached to it….even though I was in an AT&T STORE with someone who works there for at least 2 hours or more and had to make multiple calls to AT&T support while sitting with another associate just to get my old phone service back on. But no, that wasn’t enough, I was also supposed to call them back AGAIN to tell them to cancel service on a phone that was NON EXISTENT at that point.