Unwarranted spam Phone calls and spam sms's

MBD have been calling me for over 10 years over an account I have never possessed. They had stopped for three years and now they have started again. I have spoken to over 10 of them telling them that I have never had the account they talk about! But no they keep sending me sms's (asking me to pay R100 or R2146 depending on their mood) or getting their rude call centre guys to stop calling me. They used to send me calls until I asked them to send proof that I had owned the account in question, they obviously were not able to send the proof and so they stopped. This year they have started again. I now just hang up on them since they are so dull!!