Refrigerator

We purchased this refrigerator used 6 weeks ago (18.2 CF). It has now begun to freeze food in the refrigerator compartment when the setting is at 5 or above. When the setting is turned down to 4 the food does not get cold and the freezer melts into the refrigerator compartment. it also gets very warm on the back panel (open, not enclosed) when the setting is at 5. Is there a way to repair it or should we count our losses??