Still no responce on cancellation

Telkom was very fast to send reply that someone will contact me soon after my last complaint, but nothing yet, just received another invoice for the next month to pay. It is really time that Telkom look after their clients, I have cancelled this contract due to my husband took out a bigger contract with Telkom, it is not as they loose a client. How long does it take to cancel.... From December 2015 to now.... According to me I only had to give one month written notice