Don't jump to "Its low on charge; because its froze up"

A low charge diagnosis for instance can be miss read if the evaporator is iced up or has any ice in or on it. A sticking thermostat, relay, or contactor could be causing the compressor to run on when it should be off, or air flow blocked or the fan motor on the evaporator cutting off when it should be on or a dirty filter or closed vent, or misplaced thermostat sensor could all lead to a freeze up of the inside coil as well as a few dozen other things other than low charge.

To answer with any clarity we need to know is this a window, mini split type unit or central and what kind of thermostat do you have electronic display or no display just t knob pointer? Need to know what is running and what is not running I.E. Fan only; Fan and compressor only; Fan out side and compressor unknown if it is running...

And here is a real stickler, you say it has a leak and had to have a charge of refrigerant. What kind of refrigerant is it R22, R134A, R410A... And for sure was the evaporator coil still iced up when you decided it was low on charge or was it defrosted and room temperature?

All these questions have to be answered to get you steered into the correct area.