Continued harrassment!

MBD keep phoning me regarding an outstanding account, that my brother had given my cell phone number as an alternate contact number for. He has paid the outstanding amount, a whole R250. Yet these useless and *********** idiots continue to phone, and sms me daily about my outstanding, and non -existent debt! I have told them every single time to stop phoning me, to delete my number. They have now started phoning me on my office phone, this is *******!!!!!!!!! How they even got my office number is a concern on its own. I am told that calls are recorded, clearly not if I have to keep repeating to STOP PHONING ME! Do your job properly, check your records properly, or I WILL TAKE LEGAL ACTION against you. How difficult is it to listen and delete a number when you are told to, and check records of money owing? I was blatantly rude and swore at the last one who phoned and they just put the phone down, 2 minutes later, they are phoning my work number again. This is my last warning, STOP CONTACTING MY NUMBER!