[J_is_my_initial]

I work in a medical billing call center. I usually do not say either one. We have such a diverse group of people who call. If someone says one of them to me, I usually respond, same to you or you too. To show how people can be offended:
I am from the south, and I say sir and mam a lot when talking to people. I had one guy tell me to quit saying sir to him. He said he was not a sir, he was not in the military. Of course then sir kept coming out of my mouth and I tried to tell him I could not help it, that it was just a southern thing. He must have corrected me several time during that call.

when I am not on the phone at work, I guess I say Merry Christmas the most. At the old age of 46, it is just something I am used to saying.