useless contact centre

I have two contracts with Cell c, went under debt review last year now am due for an upgrade, was advised by cell c I won't be able to since am under debt review. been struggling to get hold of them to cancel the line. the customer care keeps transferring me to 084 143 that gives an error message. kindly advise why can't I renew my contract. if not please don't debit my account past the expiry date