Schreiber APP6302 Fridge-noisy and freezing food?

On return from holiday 3 days ago I noticed the motor on my fridge was really loud this has not subsided and now it is freezing my food. I have tried lowering the temperature but nothing has changed. I also note that the back wall of the fridge has iced up. Is it on its last legs? Unfortunately I cannot unplug it and try defrosting as it is integrated and the plug socket is fitted behind the machine - not clever I know but was like that when I moved in to the property. Anyone got any advice on what the issue might be? Thanks.