Cancelling contract

I have a with cell c contract I joined cell c contract I use to pay every month and their give me airtime and data so since covid I lost my job I couldn't pay the monthly fee so they blocked me on using that sim cards the were 2 of them so since last year I didn't use them no outgoing call or income call.so the problem started this month when the call me and told me that I own them money well I was not using the sim cards..then they explain and I accepted the problem so nw I want you to help me to cancel that contact for good I want want it anymore please help me.. thank you