Sounds like the repair person that said that is either ignorant of this problem, or trying to rip you off.
The first thing we check is to make sure the refrigerator evaporator fan motor is running, if so then check to make sure the evaporator thermistor is in the proper place per the service bulletin.
There is service bulletin on this problem. I'm attaching it below. Read page 2 and page 3 to make sure the evaporator thermistor is in the proper place.
Watch this video to get access to the refrigerator evaporator coil to make sure the evaporator fan motor is running and to make sure your evaporator thermistor is in the proper place.
Let us know what you find.
Jake