Cell C Cancellation

Good day. I took a contract in February and i wasnt happy with the device and sent it back the very next day. Cell C then only cancelled the contract In May 2022. Since then ive been called from Cell C wanting me to pay R11000 for the contract. I entered the Cell C store near me and was assisted to get Cell C to stop debitting my account for the huge amount. Ive received numerous ref numbers saying it is resolved. Once again 1Aug Cell C debits an amount of R12000. My name and credit history is damaged because i need to go into my bank everytime to have thr debit order reversed. Who gets to pay the admin fee for all of this trouble i need to go through everytime. Can Cell C please rectify this problem.Urgently