Product: Debt collection

I started to learn about credit and how it actually works. Step one was getting my 3 credit reports. Everything was fine on them except for when I found a collection agency ( State Collection Service , Inc ) demanding that I pay a debt to them. The account number is supposedly as follows : Account #  XXXX. I had no idea of this debts existence. They claimed it was a medical bill. I have always paid all such bills in full. I signed myself up for the XXXX XXXX site to help track my records and learn further information on what to do. I also bought several books on self-education concerning credit repair. I used this new knowledge and the tools provided to fix the issue by dispute. The items were simply removed from both XXXX and XXXX. This issue had only appeared with their reports. There was nothing on XXXX about the account at all. I thought alright perfect I can finally get better credit established no problem. The two bureaus had followed the law they are suppose to awesome. Then all of the sudden that same account which was removed by them was posted on my XXXX report dropping my score significantly. Making me unable to get the car and home loans. Unable to get the loan for the teeth implants I so desperately need. So I then decided to write the same kind of letter to XXXX   that I had previously written to both XXXX  and XXXX. I thought well they followed the law so XXXX  obviously will realize its a mistake also and remove it from my report. All of the letters I sent were sent certified mail, so I know that they received them. I asked for proof of method of verification. That would prove the debt to be mine. No verification ever came. What did come was a Derogatory remark posted onto my XXXX XXXX account. Which stated Medical, customer disputes. This further dropped my score and killed my chances of ever getting the loans I needed. I then found another approach and decided to write a letter that way. Since they had violated my Hippa rights if they had recieved medical information without my consent. ( That would be the Hippa release form required to have my signature on it in order to release such information to them. ) That's when they sent me the letter stating that no such account could be found. They also spelled my last name wrong writing Mr. XXXX, I am not sure if it was just a typo or them trying to belittle and insult me. Sorry not happening!! I also feel its necessary to point out I have no signed contract with the collection agency originally in question. ( State Collection Service, Inc ) I feel that the resolution to this problem is still simply to removed this account from my records. Has I originally had requested, As I do not owe a Bill that does not belong to me and therefore should not be forced to pay it. One more thing to add to this is the fact that I received a letter telling me that such an account could not be found. If they can't find this account it should not be negatively effecting my Credit! I have spent a lot of time and effort on getting this issue corrected. I recently learned that your site could be of great help. So I'd like to thank you for your time and effort on assisting me with this matter. 
Sincerely, XXXX XXXX XXXX Dates of letters will be on attached files.