Samsung RSA1WTH freezer not working correctly?

American Fridge freezer 4 yrs old, first of all temp -19 flashed for a while 2 days ago on freezer. Yesterday, items were defrosting in the freezer. We have turned off power supply and switched back on twice. Temperature starts at 12 degrees then goes down to 4 degrees and won't go lower. The fridge keeps changing between 2, 3 and 4 degrees.