Candy model CPCA240FFK Freezer not freezing?

The fridge seems to be working ok. The freezer is not cold enough, only a bit colder than the fridge at the moment.

Temp setting is at 4, yellow 'super' light has come on a few times over the last few days but we haven't set it to that function.

Have been told that we should defrost the freezer by turning it off for 24 hours. We have found the manual and it states that it should never need defrosting!

Please can someone help us sort out what might be wrong with it! We have a young child and really need to have it working fully all the time.