account billing not authorised

I would like to voice out my complaint. On the 12.02.16 I registered for an Intec course in Graphic Design, I paid an amount of R1300 as a deposit. 14 days later I received my study materials, during the course of 2 weeks I decided to start my assignment as I was excited. I then realised that the course is not for me then requested to change. I have since waited for the change to happen, during the course on the month an amount of R599 was deducted from my account, and I had stated that I would pay by hand, I then reversed the amount due to the fact that I had not received my new study materials for Events Management. This month my account was debited again, and I reversed the amount, because I cannot be paying for something that I do not have , now I have been receiving calls and smses telling me that my account is in arrears.