Money back and cancel

I have an issue with Telkom regarding the debit order while am not using their data since I lost their simcard more than 3 months I have visited them and ask them to cancel since they only take money in my a count and never use their services and they tell me I must pay full amount and their last deduction is R523,52 Last month took R280.38 Feb I have transfer R318 And remember I am not using their data and they refused to cancel