Our amana fridge model #. our amana fridge model # BH2055W, with a botom freezer will not maintain

Question

our amana fridge model # BH2055W, with a botom freezer will not maintain the temperature.A repairman put in more fluid, but that did not solve the problem. It will not get cold enough and does not maintain an even temperature.we are not sure whether it is the temperature contro; or if it is defrosting too often, how can we tell?