How do i stop the upper level of my Fridge from freezing?

I have a problem with the upper part of my Fridge. It keeps every thing frozen. Things like Salads, Milk, Sausage, Fresh vegetables, Cheese, Tomato sauce etc. It has been happening for a while now.
What should i do to stop this from happeninig?
My Fridge is Kelvinator Frost Free KCI 26 BFF.
Please can you advise me on what to do next.