Cancellation of contract

Good day

I would like to report Netstar for harassing me for money as they have been given my new banking details multiple times and i have now agreed to pay the cancellation fee in the new month , and they continue to keep phone me multiple times , but when they where given the opportunity to correct everything they failed too, so i have agreed to cancel my subscription due to the main reason of them failing to change my banking details over and over again , I will never renew my contract.