Outstanding amount owed on a closed up account.

I am being harassed with phone calls coming from Daly , informing me that I owe Absa R288.00 for a cheque account that I had closed because I couldnt afford the rates as I was not working anymore but attending school hense I opened a student account. When I went to ABSA to open my student account i was told that I need to make a payment of (+ -) R450 in order to open a student account of which I did pay out, but now I'm being called and told I owe the amount of R288.00 for an account I had closed in February or March. I receive six to seven calls a day from Daly. What I fail to understand is how ABSA closed the cheque account and was able to open the student account if I was still owing money. I am a second year student and exams are nearing, I do not need this kind of stress.