What is considered harassment from mortgage company?

Is the mortgage company contacting you with sales calls? Or because you owe them money?

If it is sales calls, then put your number on the Do Not Call Registry. And next time they call inform them that you are on the registry and that you want your name removed from their list immediately.

If they are calling because you owe them money, then make an appointment with them to work out a plan to pay your back mortgage. I could be wrong, be I believe that as long as you owe them money, then their calls would not be considered harassment.

I am not behind but they give me different amounts every time they call and can't tell me what it is that I owe them.

Why are they calling?

I can't get a straight answer out of them

If you are "current" with your mortgage payment, tell them to stop calling you.
They are probabaly trying to get you to refi.