College S.A Entrapping people with debt of 7 years old!

College S A. Has a debt collection agency harassing me. I paid cash for my studies. I am receiving statements for 2016 and look at the date and year where we are currently. Now they claiming I owe them. Please advise how I was not notified at the time that I owe them? I did advise that that I had no re-collection of debt. Why did they not tell me that I need to settle an amount that was outstanding at the time I paid cash. This is *******,debt of 7 years old!! Seriously!! Please refrain from harassing me as this is entrapment!