Worst service ever from nudebt

They are harassing a boss i haven't worked for in 6 years for outstanding money on my cell c accounts. I have emailed asked for call backs WhatsApp messaged them absolutely no reply whatsoever My former boss gave them my number as well it just gets ignored and keep harassing him for the money I've wasted a lot off airtime waiting for a call Centre agent to become available to no avail How must i make payment arrangements if i can't get a hold of you!! But yet you can phone 200 times a day harrasing someone who has nothing to do with the debt