Complaint sub-issue: Credit card company isn't resolving a dispute about a purchase on your statement

Re : Case Number : XXXX XXXX XXXX XXXX XXXX, OH XX/XX/XXXX To Those It May Concern : I would first like to begin by denying any and all responsibility and/or liability for this debt. It has been disputed, both formally and informally, a number of times, each of which adequate recognition of our predicament having been denied. The original reasons for the alleged charges of credit in the amount of {$540.00} through Citibank NA XXXX XXXX XXXX XXXX, was insisted upon without my knowing of the full consequence, and was presented to me in a fashion where I was unaware of the materials costs or limitations of said services, and took unnecessary advantage of my lack of understanding of critical terms. In the contents of this letter, I will insist upon and demonstrate, that Citibank NA Best Buy, and, collection efforts since then, have violated the Unfair Deceptive, and Abusive Acts and Practices Act ( UDAAP ). 
It began when we had an issue with our home personal computer. We brought the computer in-store to Best Buy, where their computer repair service, the XXXX XXXX, conducts their computer repair services. 
When we brought in the computer, they insisted on charging us a fee that was not necessarily a charge for services rendered, but behaved more like a membership fee. As the clerk described it, since most repairs have to come back again and again for repairs, its best that we have a longer set of service that will take care of all repairs so that you dont have to pay for more repairs in the future on the same item. This made sense to me at the time, though I reluctantly agreed to the three year contract for nearly {$300.00}. This is my first example of UDAAP, as mentioned above, as this charge was unfairly sold to me with the guarantee that I would not have to pay for future repairs. 
After leaving my computer with XXXX XXXX at Best Buy, within a day or two they were able to provide a diagnosis. The computer needed a new hard drive. Unfortunately though, the services that I paid for did not cover parts, just the labor. So I was forced to buy a new hard drive. This was a {$40.00} purchase. The new hard drivXXXX was left overnight with XXXX XXXX in Best Buy so that they could replace the older hard drive in our personal computer. 
Within another day or two, we received a call from the XXXX XXXX in Best Buy that the hard drive was not the reason for the malfunction, but that it was something else. When I went into the store, to talk to a representative about it, they asserted that the malfunction was not from the hard drive, as originally alleged, but from the motherboard of the personal computer. They were gracious to give me a full refund on the unused hard drive that I purchased. However, a new motherboard for the personal computer was much more expensive, and, at the advice of the XXXX XXXX representative, was not worth the repair of the older personal computer, therefore, not justifying the cost for repairs. It was recommended by XXXX XXXX staff to abandon the repair of the personal computer and to buy a brand new one, owing to the fact that the motherboard of the older computer would cost significantly more than the computer was currently worth. Since I was instructed by the company to abandon the repairs of the personal computer, and to purchase a brand new one, I requested a full refund of the now unneeded three year repair membership that was just abusively sold to me, as there would not likely be repair needs to a brand new personal computer. 
This is where I make my second reference to the violation of UDAAP regulations. Since there were no repairs done to my computer and the purchases or extension of credit through the Citibank NA Best Buy credit card, there was no reason to continue to charge me the balance of the fee. When I addressed this with the representative, I was denied any refund despite insisting upon one. This was clearly deceptive. I was unaware of the material costs or limitations of the services rendered, and essentially I paid in excess of {$300.00} against my credit card for a diagnosis of the problem. 
This introduces my final reference to UDAAP regulations, this practice was abusive. I assert that I was unreasonably taken advantage of to my lack of understanding of the risks, cost, and conditions ; my inability to protect my own interests in the matter ; and the impression that its alright for the consumer to rely on the company to act in my best interest. I was charged an unfair amount, deceived about the repairs that would be conducted on my personal computer, or lack thereof, and abused because I was unaware and forced to sign up for a lengthy membership when the computer that I brought in for repairs was not, in fact, repaired. 
Any previous charges on the credit card were paid, however, the disputed charge from XXXX XXXX for the lack of services rendered, I left unpaid. This I disputed with the clerk at XXXX XXXX and I disputed with their Manger on duty. Both told me that they refused to provide a refund because it doesnt work like that. I then disputed it with the Best Buy Store Manager, who offered to reduce the unfair charges by a measly {$100.00}, but that still meant there were greater than {$200.00} worth of unfair, deceptive, and abusive charges still being held against me. I was told take it or leave it, but we wont do anything else. I reluctantly accepted it and immediately went home to dispute it formally with XXXX XXXX XXXX XXXX Customer Service. 
I filed a dispute claim, contesting the unfair, deceptive, and abusive fees with the XXXX XXXX XXXX XXXX  Customer Service, as well as management in that call center. All of which told me the same thing. That our dispute towards the fees didnt matter and no one would hear my plea as to how the XXXX XXXX treated me with such an unfair, deceptive, and abusive acts and practices, in which I was taken advantage of by being duped into committing to a membership of repairs for which I did not require and for no services rendered. Essentially, I was taken advantage of in order to obtain money without the exchange of services and at an unfair amount. 
Since no one would honor our dispute of the unfair, deceptive, and abusive charges, I no longer do business with Best Buy, and ignored collection attempts, continuing to dispute the balance. Since then, there have been additional credit fees and interest associated with the account that nearly equal the original charges themselves. 
I continue to deny any and all responsibility and/or liability for this account under protection of Unfair, Deceptive, and Abusive Acts & Practices Act ( UDAAP ), as explained above. 

Sincerely, XXXX XXXX