Ice crystal formed in back of the refrig. how to

First of all, your freezer is freezing up DONT chip the ice!!!!!!!!!!!!!!! Either unplug the unit and allow it to thaw out naturally OR get a hair dryer or fan and let the ice thaw out. Then call us and we will be sure to get the right parts out to you to replace the defost system, which is out on your Sub Zero. We hope this does it for you and we also hope to hear back from you real soon. Ella