Cancellation of contract

I cancelled my contract with cell C at the end of October 2019. The debit order went through in November 2019, this was after I phoned and cancelled the contract for a second time. In December they deducted yet another payment , so I went to my bank to put a stop on the payment and the payment was returned by the bank. By the middle of January 2020 they put through another debit order, after I phoned and the consultant confirmed that the contract was cancelled. All bank charges that was returned on the debit orders was for my account even though they confirmed the contract was cancelled they kept on putting debit order through on my account! The customer service that I received from Cell C was absolutely pathetic and obsurd, will never again make the mistake to take out a contract with them!!! Worst service ever!!!