I’m sure it is the thermostat. How hard is it to access it and where is it found?
Cold air enters the fridge through a damper or vent between the freezer and fridge. The evaporator fan in or behind the freezer blows the air through. There is an adjustment to open and close this vent to allow more or less cold air in. That damper might be your problem but the thermostat is the knob where you adjust the freezer temp. You adjust the fridge side with the damper control.
Thanks–is there a control other than the damper that controls the thermostat?
The thermostat controls the freezer. The damper controls the fridge.