Diplomat APM 6724 Integrated fridge not cooling ?

My Diplomat APM 6724 integrated fridge is not keeping food cold milk goes off quickly.
Have tried turning thermostat in fridge up and down light still works and can hear fridge running okay and condensation running down back of fridge.
I don't have a freezer its just the fridge and its in a fitted kitchen behind a door .
Is it fixable or time for a new one? its about 6 years old