Had to shut off breaker to stop air from coming out of vents

Is the fan switch on the thermostat on "on", or auto? If its on auto, and the fan continues to run with the "heat, off, cool" in the off position also, you will need to unhook the Green wire from the G terminal at the furnace and see if the fan stops then. Let me know and we will take the next step.

Only have a mode button and a fan button. The mode button is off and the fan button is off. No auto. If I hit the fan button the word fan pops up and hit it again the word fan disappears.