Whirpool ARC7612 fridge and freezer warm up overnight help!!

Hi all
The problem I have is that the freezer defrosts and gets warm overnight and the fridge temperature gets warmer overnight aswell. However when I rotate the temperature control for the fridge to the off setting the unit switches off and light goes out. I then turn the control back onto to a setting on the scale and both fridge and freezeer begin to cool. After a couple of hours they then operate as they should and remain like this for the remainder of the day only to defrost and get warm again overnight.
Any help would be appreciated.
Cheers