Cell-C , contract cancellation nightmare

I cancelled a contract in April 2019 , as I try or this I am reversing a debit order that is reflecting badly on my credit record . The consultant at the store didn’t process or send though the cancellation, this is clear as cell c also acknowledged but they are reluctant to hold the store accountable and cancel the contract . Instead they debit my account monthly. Calls , mails and visit to the store all failed to end the contract .