Bogus Charge Turned Over to COLLECTIONS After Three Weeks???????????????!!!!!!!!!!!!!!!!!!!!!!!!!!!!

On 10/08/17, we began wireless service with AT&T and then canceled on 10/21/17 and returned all equipment to the store on top of paying for the restocking fees. This was all well within the Buyer's Remorse period and we were assured there would be no added charges and that our bill would be corrected to reflect what we actually owed for the 13 days we had service. I contacted AT&T over the phone and online about fifteen separate times throughout the next few weeks to try and resolve our bill. I was willing and very ready to pay, but was waiting for the credit we had been promised or for our bill to be adjusted to the correct amount. I even have an online chat transcript that shows the representative telling me how much of a credit should be given to us with 30 days after the start of service. Then on 11/16/17, an amount in the range of $1700 shows up on this canceled account for the returned equipment. I called that day and asked why this amount would show up, seeing as we returned everything within the correct period and paid the restocking fees. She assured me this would correct itself by 11/21/17, because they needed 30 days from the time the equipment was returned. Then yesterday on 12/6/17, I received a call from a COLLECTIONS agent! I then called AT&T again and they told me that they could see when the account was canceled and that I should never have had that amount on my account, but can no longer do anything because this is now in the collections office. I guess it is AT&T's policy to turn three week old charges over to collections, even when the customer calls multiple times to try and pay the correct amount and is told countless times that the system will sort everything out after a 30 day period. I have my return receipt, chat transcripts and phone records proving that I was actively trying to solve this problem. I will be complaining to the FCC and doing everything I can to get this resolved. Any advice on how to expedite this would be greatly appreciated. I am beyond frustrated about this and looking for any help in this matter.