Product: Credit reporting, credit repair services, or other personal consumer reports

I recently signed up for to a credit monitoring service last year XXXX. I noticed a debt that was not mine. I disputed the debt through the credit monitoring service. The creditor mailed me a copy of a credit card bill that I had not signed up for from XX/XX/XXXX that it had been sold to another debt collector in addition to a letter from them dated XX/XX/XXXX stating that a copy of the previous bill from the previous creditor was proof of validity. So I responded on XX/XX/XXXX requesting proof of validity and specified I will need a signature as proof of validity and not simply the bill. I did not sign up for this card. In response they mail me another letter on XX/XX/XXXX with a copy of another letter saying that the debt was sold. Again, this is not what I requested in my first letter. I respond again on XX/XX/XXXX, stating I do not have responsibility for this debt and to send me proof of validity. They respond on XX/XX/XXXX completely ignoring my request for my signature where I signed up, and again send me copies of statements from the original creditors ( again not mine ). I specifically state that nothing they sent to me shows that I personally signed up for this card in my response letter dated XX/XX/XXXX. In response they send another letter on XX/XX/XXXX stating that the seller provided an electronic file of its business records containing information concerning the account and print a summary at the bottom of the page containing my name, last four of social, and date the account was opened XX/XX/XXXX. No where on the letter do they ever address my question that has been the theme in all of my letters. I respond to that letter on XX/XX/XXXX in the same fashion as my other letters. A day later I receive another letter with the same exact date XX/XX/XXXX as the previous stating that they have already responded. They state my dispute alleges no new facts and includes no new information in which to form the basis for a new investigation, that they will not be conducting another investigation of the dispute pursuant to 15 U.S.C. Section 1981s-2 ( a ) ( 8 ) ( F ) ( i ) ( II ) of the Fair Credit Reporting Act and that if they continue to receive subsequent correspondence from me regarding a dispute that has already been resolved, they will consider my inquiry answered. No further replies will be forthcoming unless I provide the information they need to assist me and they consider this matter closed. None of the letters I have received from them ask me for any further information, so what exactly are they talking about? On the contrary the letters I have sent to them all ask the same question and they won't answer it, yet they send letters with no questions and send me one stating I didn't provide information for their question. They never answer the one question. I explain to them how this is effecting my credit report in a negative way and they do not simply read the letters asking for proof of validity with my signature. They then send me another letter dated XX/XX/XXXX I received yesterday XX/XX/XXXX ( all of their letters are dated yet I always receive them far from the date stated on the letter, I am only in the next city over ) stating that they requested additional information pertaining to the account ( they never specify what information ) They then state they can not complete the investigation, and since they have not received it they are terminating the dispute. Once reading this I log into my credit monitoring service, and the debt is still their with the remarks " dispute resolved ; customer disagrees '' I am pretty sure disagree and resolved would be considered an oxymoron. It wasn't resolved they never answered my question, and are closing the case based on the fact that I didn't answer questions in their letters that they never asked. In addition this is for a debt of {$440.00} that is not mine.