Our heat will not turn off.?

We have hot water heat. Our downstairs heat is working properly but our upstairs heat will not turn off! We took the front part of our Honeywell thermostat off (thinking if it wasn't connected, it couldn't call for heat) but that has done nothing. It is over 80 degrees upstairs. Our boiler runs on oil so all this extra heat is wasting money! If anyone could help, it would be greatly appreciated!