defrosting freezer?

I have moved house and the fridge/freezer is an integrated unit. The freezer looks as if it has never been defrosted, but I cant find a switch to switch the freezer off. There is a button to the side of the fridge dial in the fridge. Does this switch off the freezer for me to defrost it? I don't want to mess with it in case it isn't!

Judith
December 2010