Disappointing service

Last month I had sent an email to CellC who are my service provider to query a contract that had continued pass it’s end date and I was given a call and I told the consultant that I’d like to cancel it which she said she will do. On Wednesday 10th April 2019 I received an sms alerting me that my contract has been retained and that was not our initial agreement. I never gave them authority to retain the contract but they continued and did it either way. Was promised a call back regarding the resolution of this issue but still nothing