GMR — I was charged higher by Air India for excess baggage

I was travelling from Delhi to Bangalore from Air India (AI-502). While weighing my luggage, they told that I have 2 kg of extra baggage weight and I will have to pay 630 Rs per kg for extra baggage. It was clearly bannered by the GMR that there is a charge of 100 Rs per kg for baggage. I told them that I just have to pay Rs 200, Air India staff told, “no mam, you have to pay Rs 1260 for 2 kg of extra baggage. I told that it is written everywhere, they told no that is for courier service, they lied to me and overcharged me. I had paid them via googlepay, attaching screenshot for reference.