how can i fix refrigerator model apm 6816?

I have a hygena diplomat integrated fride freezer model 6818 for more than 10 years. it has given me good service, however since last 4 months the fridge compartments get too much of frost ( even when thermostat is set on lowest ( 1), every day I have to scrape the ice. Do you think thermostat is faulty or something else? what can be done?
Shirish