prestige fridge freezer?

hi there. i have a prestige fridge freezer.model PRT 295 FFCS. the problem i have is that the freezer is not going up to thhe temp-18. but ive had to turn the fridge off due to the fridge freezing. ive had to throw all the food out in the freezer. and take all the fridge food out of the fridge cause it is starting to freez. please can you help

cheers
pete