Product: Debt collection

While a consumer of XXXX XXXX XXXX mobile and home services, I incurred a continued obligation to pay for services with my bill cycles typically running through midmonth. During the period of XXXX XXXX, I did not pay my bill timely and as a result incurred a small fee for a late payment. Following that, I paid my bill for XXXX and XXXX XXXX jointly paying a bill of approximately XXXX dollars as my monthly bill vacillated between XXXX-XXXX dollars at that juncture. Shortly thereafter, I cancelled my wireless account and my home account in XXXX XXXX ( though was continued to be newly charged for home billing through XXXX XXXX ). Following the closure of the wireless bill, I received a statement that I owed no balance for which was correct based on my previous payments. However, shortly thereafter I received new bills indicating that I still owed for XXXX XXXX. I called XXXX XXXX XXXX and was directed to XXXX different departments with varying results. None of the departments new how to handle my call based on state and call center and could only see the end result that I owed the amount. After I explained that I contested the amount based on previous payments, the individuals became confused and transferred me to different departments. Eventually I ended up at the wireless department and they confirmed that there should be no balance and indicated they would notate the account that I was wrongfully charged. 
Afterwards, XXXX XXXX XXXX sent me follow-up bills saying I still owed this amount and we would repeat this exercise several more times with XXXX siloed systems and call centers all being unable to resolve the issue until being transferred to wireless where they would again confirm that I did not owe the bill and that it was a mistake and a notation would be put in the system not to collect. After several more go arounds, in XXXX XXXX, XXXX XXXX XXXX sent a final notice indicating they were going to sell the invalid debt despite repeated follow-ups by myself and acknowledgment from its agents that the debt was fully paid and invalid. At approximately XXXX XXXX XXXX, I called again and spent several hours on calls with several agents who teleconferenced other agents in to resolve the silo issue and invalid debt to connect the front end and back end agents to discuss why the debt should have never existed, that it was paid originally, and that I continued to be pursued for debt charges. Agents from multiple departments sat on the phone, exchanged ID numbers and worked to update the system to stop charges on the account prior to being sold to a third-party agency as they agreed that I paid the appropriate amount and should not be charged further. This time I was assured that they had resolved the issue and that there would be no more attempts to collect the invalid debt. 
Following that, it appears that XXXX XXXX XXXX sold the debt to a third-party collection agency and I was informed at approximately XXXX/XXXX/XXXX with a letter dated XXXX/XXXX/XXXX that I was to pay the debt or incur a negative bureau reporting for the money disputed by XXXX XXXX XXXX. At this point I write this letter to dispute the bill in its entirety and send to the FTC, CFPB, the debt collector in question, and will send a copy to XXXX XXXX XXXX directly as this is an entirely invalid debt from which XXXX XXXX XXXX has continued to acknowledge was invalid through discussions with its agents and they attempted to stop the continuation of this debt. 
As this debt was paid in full upon original receipt, XXXX XXXX XXXX was contacted multiple times and not only acknowledged that the debt was not to be paid through its direct agents and confirmed through multiple departments and proceeded to sell the debt, I believe that XXXX XXXX XXXX has violated 15 USC 45 under both the deceptive and unfair prongs of UDAP. I believe the sale of the debt & involvement in the debt collection market should be held to the corresponding standards of 12 USC 5531 & 5536.