My Maytag Plus refrig. Is set on the coldest setting and doesn't keep things cold at all. Help.

If the t-stat is turned up all the way, then check the evaporator, it may be freezing. This could be something you could service, if its not going into defrost like it should, then it could as simple as replacing a defrost timer, however sometimes evaporators will begin to freeze over when they are low on charge, for this you will need to call for repair.