Billing me for an upgrade I never received

I tried to upgrade my phone but it never went through, as ATT contacted me in my ATT inbox saying it must be canceled.

So I canceled. Never received a new phone. Still using same walmart phone.

The problem is they charged me the upgrade fee. I called. Got sent to different depts. and disconnected from. At one point they connected me in the wrong language. Then I finally called again and the rep said she was talking to her manager and that they will take the upgrade fee off.  

THEN, it never happened. So I went online to my billing info, i saw a section that allowed me to dispute the charge. I did so. It worked...for a day I guess, because the charge is still there. I paid my bill a couple weeks later which INCLUDED the UPgrade fee.

I tried disputing it again and it said something to the effect of: You cannot dispute this because it is a valid charge. 

I have no upgrade. NONE. Im using a walmart phone same one I had since my last phone I was still paying on went to lala land and they said my insurance EXpired, so I had to get a walmart phone, (Separate subject)  and yet I have been charged. I am so tired of calling.

Anyone ever have to pay a (Edited per community guidelines) fee just to get a charge removed? the (Edited per community guidelines) charges more to write the letter...but I almost think its worth it for my poor piece of mind. :(

I used to brag about ATT having outstanding service. I never wanted to change phone companies because I loved the service. I change my mind lately...i am so upset.

Any help out there?? :(