Oklahoma Debt Collection Issues

I live in Oklahoma and I signed a rental agreement with two other people for one year. The rental agreement was for one year and for anything past that I would have to sign a new agreement. After my one year was up I moved out of the place in the summer of 2008. The other two stayed behind and began a new agreement with another person. In 2009 I was contacted by a debt collection agency stating I owed rent for some period in 2009. I advised them that I had not lived at that residence during the time they were trying to collect for and I spoke with the manager of the property who assured me that my name was submitted by accident and she would clear it up. I was not contacted on the matter for another year. I received a phone call in 2010 from a different debt collection agency stating I owed the previously mentioned amount. They stated they would take "legal action" against me unless I paid them in full. I explained to them the situation, told them I wasn't going to pay, and asked for contact information which they refused to give me (odd seeing as how they wanted me to some how send them money). I was not contacted again until today (8/30/2011). I received a phone call from a very rude lady who demanded I answer her questions about wether or not I had hard evidence that I was not responsible for the debt. She claimed she worked for a debt collection agency but that they did not "buy" claims. She told me that due to federal law they were required to block their phone number from showing up on any phone. I requested she send the company's contact info to my address at which time she became highly agitated and stated I had to write them before they could send me anything. After much arguing and her flipping out because I did not have an ink pen handy I finally got her to agree to send me the company's contact info.

What should my next move be?