Harassing me for Payment I do not owe

I received numerous SMS from TFG to pay R58 which they say was overdue. I have had my account for more than 30 years and have never been in arrears and in fact I always pay in advance and more than my monthly instalment. I called the contact centre twice and was assured it will not happen again. I have since received 2 final warnings to pay R58, threatening SMS messages. I cancelled "my kitchen" subscription 2 months ago and I suspect that they still charging it when I was assured it was cancelled. This is in direct contrast to the NCA and recent findings of charging for magazines that no-one needs. I need this resolved immediately. Very, very disappointed.