Very bad telephone etiquette. Very rude

I received a call from a guy called Lefhuno from Pretoria branch asking me when am I going to pay a certain medical bill which had previously explained to him that it doesn't belong to me and that I was erroneously charged for. The guy was so rude, doesn't want to listen when spoken to. He dropped the phone on my ear . I phoned him back he said "I will show you I can drop it again" and he did. For the second time. I was left buffled. Reported him to their complaint division, they promised to call me back, still waiting even now.