Account activated and immediately cancelled by BestBuy but received bill from At&t

Hello,

BestBuy at&t rep activated my account (bogo offer), but was unable to port the second number. So rep called at&t and cancelled the account immediately. But after 2 weeks I got a bill from at&t, with full iphone price, acitvation and taxes. 

I called at&t and they advised me to go to best buy store and have the rep call and open a case confirming that I ddin't receieve the device and the activation was done by mistake. Which they did and a case was opened, and today when I called at&t to find out the case status to my surprise I was told the case has been rejected. (and the reason was best buy at&t rep didn't provide the rep number..etc). When the case was opened all the requested details were provided by the bestbuy rep, and today at&t rep infomed me that they didn't note down any of these details. 

I am going to go to the bestbuy store again today, but this is something not resoanble -  as advised by the rep I went to BB and they provided all the rewuired details. I will have to do this all over again with no gurantee that the issue is goign to be resolved.

Amout on account is (which I don't owe) due today and I hope at&t address the issue, pls let me know if providing the case number/account number helps in resolving the issue