How full is freezer, and reg compartment? How open is the path of the blower in the freezer compartment? Give the blower a clearer path to do its thing.
Perhaps the thermostat is stuck in the open position (maxing out coldest). If I were looking to try something free and easy for a repair (than calling appliance repair), I'd spin or work that thermostat dial back and forth and see if you can hear a tiny click (relay) when it passes the temperature that normally would turn it on.
Short of that, I'd check to see if the gasket for the freezer and reg compartment are clean of any dirt, debris or something that might keep the door slightly open.
apropos of nothing...move the fridge about 3/4 of an inch from the rear wall. They need a proper unblocked ventilation area to disperse the heat from the rear. This is a general tip., though, not causing your problem.
The last (best) thing I'd do (probably the one that would fix), is call repair.
I Always open a beer or beverage of my choice while they work. It's like watching World series with Red six winning. It coasts money but you know it's a great adventure.
P.S. If you're exceptionally adventurous and handy, remove the thermostat if that gasket procedure didn't fix it,. then with a multi-meter see if when you turn the dial the switch show resistance and then zero as you dial the switch up and down.