The american frost free fridge freezer is not working. ?

There is ice on the back of the freezer & not freezing hence the fridge is not cold as usual?
The name of manufacture on the door is Gibson (is a local brand for GE or frigidire or Kelvinator in the middle east.
When this happened before the approved repair was to change the thermostat & the fan as well as replacing thre freeion. Who has these parts & can repair the unit.