My name is Ivor , I hope I can help you with your problem.
I trust you have tried altering the thermostat setting inside the fridge?
Also I trust the freezer is working ok?
Now from the back of the fridge inside under the cooling plate, there should be an outlet where defrosting water collects and is let out through a tube, this tube goes down the back of the fridge and is evaporated onto the motor housing.
If this tube or hole is blocked water can collect inside the fridge compartment and freezes up.
Perhaps you can check this out and get back to me with what you have found.