City Power keep pestering me.

I live in CAPE TOWN!! City power pester me day after day after day!! On countless occasions I told them that they have the wrong number, but it does not help. So somewhere is a customer that are hugely frustrated. How do I get my number off their system so that they donk call and send me SMS every day? No use talking to the person that call or the supervisor. I'm about to get very rude about this pathetic incompatance!