Contract expired

I am one of the individuals who hate complaining but what Telkom mobile is doing is unbearable. I had a contract with them and it expired last year 30 November 2016. I have made numerous attempts to cancel it using email ********** but I had no success. My salary goes through on the 15th every month. The sad part is that those ******* deductions that they are not consistent, sometimes they go through on the 25th, 30th, 31st, 10th etc and they bounce. The charges on my account are very extreme because of this. Currently my December charges are sitting at R1300. I'm tired of paying Telkom Mobile while as I'm not benefiting from them. We had a good relationship during my contract & I never thought they were capable of such ruthless action.