My refrigerator (not freezer) compartment routinely gets well below freezing and also goes above 40° F. I just had a can of soda explode overnight 
Coils are clean, I’ve called the manufacturer (useless idiots), and they had a “technician” (i.e. a button pusher) come out and check it (also useless). Any thoughts?
Thermostat
Damper if it’s a freezer/refrigerator combo.
Leaky gaskets
Lack of contents
Replace with adult cereal malt beverages, they have much lower freezing points.
It is a combo. I don’t mind replacing the thermostat on a punt…but the button pusher pushed some buttons and said “the diagnostic check indicates everything is working correctly.” I said “is this unit in particular designed for the refrigerator compartment to go below freezing until something freezes?” and he replied with “the diagnostic check indicates everything is working correctly.” And I said “could it be the thermostat?” and he replied with “the diagnostic check indicates everything is working correctly.”
I try to keep some “ballast” in the thing (water bottles full of water) as I don’t have need to keep it super filled:
But for the most part it is mostly (?) occupied most of the time:
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Screw it…it’s America…I’ll just buy a new one.
NEW ONE!!!
I kept trying mark Freddy and Dave’s answer both as the “answer” and kept going back and forth because I couldn’t decide which one was the better answer. Good ol’ Discourse Nanny-Bot (aka DNB) put a stop to that right quick, though.
Make sure that the circulation fan at the back of the fridge is clear and running
At least you’re keeping well hydrated!
