Does your aircon need a gas top-up?
Updated
A sealed aircon system should retain refrigerant. A warmer room does not by itself prove that gas is low: dirty filters, obstructed airflow and equipment faults can cause similar symptoms.
Diagnose the cause first
Describe when the problem began, which rooms are affected and any leaks, noise or error codes. A technician can determine the checks required.
Repair leaks rather than repeatedly topping up
A top-up cannot seal a leak. If refrigerant is low, discuss leak testing, repair and a recharge appropriate to the equipment. Do not mix refrigerants or attempt DIY charging.