Debt Collection - Wrong Number!

I keep getting sms's and phone calls chasing a Mr Ryan (on my number) for an outstanding debt with ABSA. Despite me telling them many, MANY times that I am not Mr Ryan and have never heard of him they just keep harassing me. How much time and money are they wasting every single time they contact me? Is ABSA aware of how much money they are wasting? I presume this wastage is passed onto Absa in the form of charges for services rendered. I've decided not to bother wasting any more of my time and energy explaining to MBD that they have the wrong number. No. I will simply keep blocking all of their numbers (and the have a lot) until one day they will finally get the hint.