Before changing the thermostat, was the coolant level low?
With car at normal operating temp, command full hot....if no heat, feel the inlet and the outlet hoses to the heater core....if outlet is cooler(both should be hot), then the core is partially plugged and should be reverse flushed to try and get the crap out of it....
If both hoses are hot, then you have to check the actuator for the temp door.....command full hot to full cold and back and see if the actuator moves...