Compressor freezes up at night and some during day.

Have the leak located properly charged unit and cleaned would like to know the part of the country your in this time of year it is not a low ambient problem
IMHO have the evaporator, condenser and blower wheel cleaned. Good luck Tom

You are being ripped off. The ambient (outdoor) temperature at night is low and therefore proper condensing does not take place causing the refrigerant to pool in the condenser and starving the evaporator. This causes a lower temperature in the evaporator resulting in "freeze up" which is often mistaken for a loss of refrigerant.
The proper thing to be done is to block off the condenser air causing the high side pressure to rise until the eqivillant of 110*F condensing temperature.
You can also install a low ambient kit which will cycle the compressor off when the temperatures fall