28 month contract from telkom!!!!!!!!!

I have a telkom mobile contract with telkom mobile.However the contract ended December 2017 but still they have been debiting me without fail from my cheque account. I have forwarded the debit order cancellation form on the 04th January to the the email ********** and have not received any feedback since that date. Can somebody please cancell the debit order because already for the month of april 2018 i have received a statement which indicates that you guys are going to debit on my paydate. This is so frustrating and shows how telkom mobile is pathetic.I have played my part throughout the contract by paying every single month for the past 24 months. A 24 month contract that ended up being over 28 months!!!!!!!!!