Product: Debt collection

This began when I subscribed to XXXX XXXX internet service. 
In my initial contact with XXXX XXXX there representative told me in order for them to supply internet service I would need modem. The rep gave me a precise description of the modem. I found and purchased that exact modem. 
However, when the installer arrived to do the install he looked at the modem and said that is the wrong modem and I can not connect your service with that modem. I explained to him that their rep told me to buy that modem and showed him my notes with the reps name and contact information. He said, OH, they do n't know what they 're talking about, and went on to tell me which modem I needed, and I could order it from XXXX which I did. At that point I had over {$250.00} spent on Modems and they made no offer to cover my costs on the wrong modem I had purchased per their reps instruction. 

So the installer hooked up the service with the which worked for about 2 months and then it started to go down every few days. About XXXX or XXXX times they were able to get it working again. The next time it went down however they were not able to get it working again. They said that they would need to come out and go inside my house and see what was wrong with my phone lines and that it would be a minimum charge of {$250.00} and could be more, perhaps even {$500.00} or more depending on what they found. I asked them if I paid there fee for coming out and doing what ever they were going to do if they would guarantee that I would then have reliable service. They said they could make no such guarantee. I also explained to them that my phone worked fine. I checked with my phone company to see if there could be something wrong with my phone lines considering the fact that my phone worked fine. The phone company said that would not be the case if my phone was working fine. I called back to XXXX XXXX and told them the phone company said my phone lines were fine and to please restore my service. I made several more calls to XXXX XXXX over the next couple months and continued for that time to pay their bill even though I had no service. On my last call I told them that they were in breach of the contract because they failed to provide the service I had been paying for, and that I would stop paying their bill if they did not restore my service. They said again that my phone lines had to be the problem and they would come out and try to fix the lines for the minimum charge of {$250.00}. I said I was not willing to risk another {$250.00} and perhaps more on the basis of what I had found out from the phone company and that they would not guarantee I would have reliable service even if I paid their additional charges. I told them to cancel the service and to stop billing me because I was not going to pay a bill for non existent service. So I stopped paying the bill because I had no service but they continued to bill me for another 4 months. They then sent me to collections for that additional 4 months of service which I did not get, just as I had not received the last 3 months of service which I had paid for. So the net result is that I paid over {$250.00} for XXXX modems which are useless to me, I paid for XXXX months of service and received less that 3 months service. So altogether I paid {$250.00} for modems, about {$180.00} for XXXX months of service, and I now have a collection on my credit report that is negatively affecting my credit score such that the mortgage I am applying for is going to cost thousands of dollars more due to this collection showing on my credit report for {$120.00}. In reality XXXX actually owes me money. 
To make matters even worse the collection appears on my credit report as an XX/XX/XXXX occurrence, when in fact this all took place in XX/XX/XXXX. 
The collection agency, at no time has supplied any documentation that this debt is accurate as reported.