The warranty on a fridge is usually one year on parts and labor.
The compressor could have 5 to 10 years and the sealed system 10 years.
This is all determined by the manufacture.
If the freezer is cold but not freezing check the coils behind the panel in the freezer.
If there is an ice build up on the coils this will cause your problem.
This would mean that the defrost timer, defrost heater,or the defrost bi metal is faulty.
Here is a link to your fridge model bx21tw. | 
Freezer not freezing only cold air ?? 
