fridge freezer beko cda660fw con u tell whats wrong?

my fridge freezer beko cda 660fw frost free, freezer doesn't freeze any more or get cold at all . i have tried the defrost thermostat at the back but it doesnt make any difference were can i get a new one or is there something else wrong i have only had it 2 yrs i think the comprssor is working as the fridge is cold but the freezer does freeze could this be down to the defrost timer ? or something else