re: AC/Heat issues

I’m having the opposite problem. My heat won’t shut off once it reaches the set temp on the thermostat. Air handler is one week old. Thermostat otherwise works in every other way it’s supposed to, including when the ac is on. It shuts off for that. It’s not due to the cold either. I was testing it yesterday before the front came through and the heat wouldn’t shut off then either. Very strange.