samsung RS21FCSV freezer side not cooling properly?

We have had this side by side fridge freezer for 3 years. The fridge and freezer both stopped working completely. We were advised to turn it off for 48 hours which we did. When we turned it back on the fridge is now ok at 3°C. The freezer is supposed to be -20, but fluctuates wildly between -16 and +2 (according to the display). The thermometer I put inside reads about -5 usually. What is wrong with it?????? Can anyone help please? We are having difficulty finding someone that fixes these samsung side by sides.