Report to Credit Bureau when no contract? (long)

I hope someone can help. I had a pest control company come to my home last year regarding termites. The rep gave me an estimate to take care of the potential problem. I showed him the estimate I was given from another company and he said his company would beat it. A few days later I called to arrange the first treatment, and sign a contract. The tech that showed up gave me a contract that was $500 dollars more than the one I discussed with the sales rep. He called the office and the person in the office told me to give the tech the $400 deposit to start the first treatment and that they would send out the new contract with the proper cost. A few weeks later, no contract. I called them and they said they would send it. 2 months later, nothing. Another call to them, only this time the so called owner gets on and tells me the rep should not have said they would beat the competitors estimate. I explained that they already had $400 of mine and that I would not pay any more until I had a contract. 5 weeks later, the owner leaves a message that they were still awaiting a payment to continue their service. I call him back and tell him again that I insisit on a contract to protect my rights. He tells me they have a signed contract and that he will sue if I don't pay. I told him to fax the signed contract to me as proof that I signed it. The only document I signed was the confirmation that the sales rep had explained the precautions and possible problems regarding the "CHEMICALS" they would use. The other document faxed over has the "Contract" header, but is clearly un-signed and not approved. When I call back and to point this out to the owner, he won't get on the phone. 2 weeks later he leaves a message that he doesn't want to go through the process of sueing me, so let's make some kind of deal. I call back and tell his office manager that I will only accept the original contract/cost discussed and nothing else, besides the fact that I had already paid $400 dollars. A few weeks later, he has his collection agency call me and send a letter. I call the agency and fax my proof to them that there is no contract. The collector says they see the problem and will be in touch with the owner. That was 4 months ago and I never heard fro them again. Now I go for a new car loan and right there on the report is the pest control company. How did it get there if they didn't even have my social security number? How do I get this off now? It seems like any company can just put a mark on your credit with just a name and address. Any help is appreciated!