I didn't have heat downstairs so I had the circulator pump replaced , purged, drained and refill. the pipe for heat is very hot but if I turn the thermostat on to 80 it wont go beyond 70 degrees. I put 3 thermometers in the room and they all say 70 . why wont it go up?

"I had the circulator pump replaced..." was that your decision, or a heating professional?
Usually the first step is to check for air in the radiators. You don't say what kind of heating system you have, so I'm just guessing. (steam rads, steam baseboard, hot water rads, hot water baseboard)
Sometimes someone turns one radiator down to save on heat.
Sometimes the thermostat just wears out.
You can't get answers online from what little you have told.

its steam heat the psi is on 15 . it was the heating specialist who said it was the pump when I told him that the heat doesn't go above 70 downstairs he said make sure the vents are open and clean no dust. I did that,
don't know what else to do unless I spend more money and ask someone else to take a look.

I don't know where the real plumbers are this weekend, but I'm confused.
So I'm guessing that your steam boiler supplies steam to radiators, not baseboard.
You don't say if old one pipe, or two pipe. Or just in general how old this whole boiler is....

Call the installer of the pump and MAKE him come back and MAKE it do what he said it would do, no fee!