Inundated with nuisance calls from Nimble Collections looking for another person - you have the wrong number!!!!

I have been inundated with calls from Nimble Collections' call centre for the past two weeks and each time they ask to speak to a Mr. Nicholas van der Walt - each time I tell call centre that I don't know such a person and they have the wrong number.

I have repeatedly asked to have my number removed from their system, and they still call. Very frustrated with Nible Collections!