2008 Suzuki Forenza air condition

Oil changes have nothing to do with the air conditioning system. Most likely there is a leak in the system and the refrigerant has leaked out. There's a low-pressure cutoff switch to prevent the system from running and potentially drawing in outside air with harmful humidity in it. Have your mechanic perform a thorough leak check of the system. The quick checks they do when they recharge the system will not usually identify a very slow leak that takes three months to empty the system.