DSTV Impossible to OPT after several attempts, not even a customer

DSTV has not been able to stop harassing me. I have tried to opt out of their communications but still receive it. I have been contacted by them previously to advise that my cell number belonged to a previous customer and still receive SMS's to settle accounts and reminders and marketing materials, in spite of my opt out efforts. Trying on their chat bot on the website sees me wait 20+ minutes then the agent keep asking my personal details to check the system for my account number. This is totally unacceptable as I have never been your customer but cannot be left alone by you! I answered your calls, stating I am not a customer few times already. How many other companies are you selling my contact number to for marketing?

STOP HARRASING ME!!!