Unwarranted calls

I am not and have never been an African Bank client. However, for the last couple of weeks, my phone number has been inundated with calls from this bank, in- and outside of business hours, looking for someone I've never heard of. The more I ask to be removed from this database, the more the calls roll in. 2 agents actually insisted on detail of how long I've had my number (which is in excess of 15 years!). I have on numerous occasions asked to be removed from your database. Please action this request immediately.