Refridgerator. My refrigerator only freezes the bottom section of the unit. it is an upside down

Question

My refrigerator only freezes the bottom section of the unit. it is an upside down refrigerator . in as much that the freezer is at the bottom and the refrigeration section is at the top. my prob is that the bottom section works ok but the top section does not . I have changed the thermostat and it has made no difference . the compressor is always running and it seems to be barely ticking over