If the freezer can't maintain a temperature of 0 degrees F even though the temperature control is set to about the middle, then you have a problem. The compressor could be bad (in which case the refrigerator is worthless, replacing the compressor would cost more than you paid) or the thermostat could be bad. In either event it needs to be repaired or discarded. Bring it back and let them fix it or give you your money back.

It seems like my freezer is only able to get as cold as my fridge. My fridge works great but nothing will freeze in my freezer. The fan is working and the vent isn't being blocked by anything. I bought it from a used appliance store about 2 weeks ago, I can take it back but its the nicest one I can afford and I don't wanna trade it in for one that could possibly have more expensive problems. What could be wrong?