Hotpoint fridge/freezer top section too warm. Bought this second hand. There is an LCD display

Question

Bought this second hand. There is an LCD display which gives the temp. It shows the top section as being 19degrees - and it is warm in there. I have tried lots of ways to get it cooler using the buttons (I can set watches ok) but it doesn't seem to make any difference. I suspect the chip is failed ... if it is this can I get a new one and where from?thanksjohn