Forced Payment

I signed a contract with virgin active about 4 months ago and I told the promoter that I am unemployed hopeful to get a job soon and I am a student. I paid R160 for registration but however I attended only once and after 2 weeks I realized I could not afford and I wanted to cancel my contract immediately. When I called to cancel they told me that I must pay R2000+ (Which I didn't have) because i should have called 5 days after the registration and it was mentioned to me by the promoter he did not explain anything to me. I started receiving calls and emails from the MBD demanding the R1198.35 (Monthly installments) and I told them I cant pay, I am a student, unemployed, my mother no longer working and I still owe my university fees, that is what i told them but they still demand money from me and I don't know what else to do, i cant find a job either. Please help me.