Overcharging at KR Puram Metro parking

Has anyone noticed being overcharged at the KR Puram metro parking? The board says ₹15 for the first 4 hours and ₹5 for every extra hour (max ₹30), but I’ve been charged more almost every time I park there. Yesterday, I parked for 2 hours and was asked to pay ₹20. When I asked for a receipt, the attendant claimed the POS machine wasn’t working. This seems to be happening to a lot of people. Is there a way we can address this? Would love to hear your thoughts or experiences.