Telkom failed to cancel my contract

At the end of my contract, I sent a cancellation e-mail on the 5th Dec 2018. However, Telkom failed to cancel my contract as per my instruction. They haven't said anything to me in writing or verbally. I never got any feedback even to give me info. I am dissapointed about Telkom. They'll keep taking my money every month, even after I cancelled in writing. I'm very dissapointed. My e-mail address is ********** & no. ********** 3