It could be that your freezer door gasket is not seating properly and allowing outside air to infiltrate the freezer. You can easily check this by placing a light source inside the freezer compartment and checking to see if you can see any light around the gasket. It could also be that your refrigerator is "frost-free" by having an electric heater that encircles the freezer compartment (you can't see the heater). If this is the case, then there should be a switch that you can use to turn on/off the heater. To get rid of the frost buildup, turn the switch to the on position. My guess is that your freezer door gasket is not sealing properly but replacing a door gasket is a fairly simple process. If your refrigerator is still under warranty, call the retailer and have them fix it.
Paul
August 2007