Not a client, but constantly harassed

I am not a Standard Bank client. I have never been a client, and at this rate I never will be. <br> <br> Over the last 6 weeks they call me 4 to 5 times a day, send innumerable text messages at all times of the day, insisting that I have a home loan with them that I have defaulted on. Every time they call I have tried to explain to them that they must have the wrong number, and asked them to stop calling. I have been to their branches four times in person to try and get them to stop calling. They have not stopped. I feel that this is beginning to verge on harassment.