Insults from debt collections agency

I constantly receive phone insulting and threatening calls from this company , and they claim they are acting on behalf of Truworths store. Even though I acknowledge that I do owe aforesaid store, I feel that collection procedure by their agent is unprofessional and *********. They always call me at odd hours of the day and when I object, they become agitated and in s process insult and threaten me with legal action. Yesterday, Friday, 09-10-2015, one of their call centre agents swear at me when I objected their late night unsolicited call. I feel like my dignity has been impaired and even my family members are traumatized by that call. I just wanna complaint about their unprofessional behsbo as I believe this is a clear harassment from their side.