Gas and Oil Home Heating Furnaces - Furnace runs to 68F max

I have a new York furnace -- multi stage variable speed. The thermostat is new -- honeywell -- supports single stage furnaces only. When the t-stst temp is set at any temp higher that 68f the furnace runs upto the room temp reaching 68f and then turns off. The furnace wiring diagram to t-stat shows two ways to wire to a t-stat -- single stage t-stat and multi-stage t-stat. Mine is wired for a single stage t-stat . Under this setup am I not getting the furnace 's dual stage? Do I need a t-stat that supports multistage? I can get a honeywell for $85canadian this week on special.
Firoz

You dont say why a new tstat? New furnace call the guys back and fix it? Take and jump R to W and see if it will keep on running. If so its in the tstat . If not its in the furnace. Dont know what tstat you have there but on some you have to make sure that it is set right on the back for what you have there Gas, oil ,or electric

ED ;)

Used another t-stat as well. Same problem. By the wat its gas.
Firoz