My question involves collection proceedings in the State of: Texas

I attended the Art Institute of Austin in 2010. I only attended for 3 weeks. I had federal aid and upon withdrawing from school the federal aid was refunded. I never heard from the school again.
My reason for withdrawing was because I could not afford out of pocket costs the school wanted. The school is claiming that I owe them $6544.96 which is absolutely absurd. They sent me a ledger showing that they refunded the government the money and charged me instead. They also claim they sent my debt to collections, but there is nothing on my credit report. I want to dispute the charges, but the lady I spoke with in the accounting office wouldn't give me any help. She just kept insisting I owe the money and I need to set up a payment plan. What do I do? I only attended for 3 weeks, I was under the age of 25, and I come from a lower class background. I average $10,000 a year in income. I barely scrape by as it is and now 7 years later they are asking for money. Its not a third party, its the actual school.