I take a lot of calls at work and people are more apt to say things like this to me on the phone.... On the phone or in person I tell them the same thing.

This kind of conversation is not appropriate for the work place so I am going to have to stop is here. Then walk away. Or if I'm on the phone they get one more warning. I ask if they would rather talk to my supervisor. If they are just repeatedly insulting me to try and start a fight I end the call...

Some people will always just try and start trouble. There is no reason to get sucked into it.