Debt collectors harassing me who can help me to take legal action against them?

DO NOT IGNORE: Pmt on ur bought CAPITEC acc is crucial. Pls call MBD INC. on *** today. ***

This is not my account and I have called these attorneys 5 times already to remove my cell no from their database as clearly the previous user of this cellphone no has this debt not me as my surname is not Africa either..... who can I contact to take legal recourse against this harassment and abuse I am being subjected to? And debt collection phones calls while I am at clients which is affecting my professional reputation.