AvanteUSA Harassing calls about a debt I was told had been dealt with almost 7 years ago. Houston, Texas

In 2006 I received some debt collection calls about an online college (University of Phoenix) which I had not agreed to attend. I was told that it must have been me, and that I had to pay, so I asked my mother for help because she is very good with accounting and dealing with financial issues. Within a few months I was told that the problem was dealt with and I did not need to worry about this debt anymore. Now after almost 7 years without hearing from anyone, I am being called regularly by Avante and each time they deal with me differently. With the first call the person calling me told me that if it wasn't my debt I could call the university of Phoenix and talk to them about it; so I did, and after numerous attempts I finally reached someone who told me they would send a form to me in the mail to dispute the claim. I never received anything from them, and the last caller from Avante told me that they had information from the university saying I called and was refusing to pay so they need to try harder to collect. Throughout this ordeal they have been calling and harassing me on a regular basis. I am just sick of this, and I am a struggling student at a real life university (UofA). I don't have the time or the money to waste on this nonsense. They have even called my mother who lives halfway accross the country.