Whirlpool Customer No Care Service

Amidst the Covid lockdown my Whirlpool Refrigerator ran out of Gas on 23rd June. We found no cooling and milk and vegetables were spoiling. I reached out to Whirlpool Customer Care on 26th pleading with the Customer Care person to fast-track the services which he promised and same day I got a call from a service center person who informed me that he was in our vicinity and would I be available for him to look-up the fault in the fridge. I told him that apparently it needs Refrigerant Gas refill and since I was home, I asked him to come anyway thinking that he would do the needful. An elderly person came wearing mask and gloves and took all safety measure for Covid protection. After checking the cooling by putting his hand inside the fredige and freezer, he proceeded to write out a long prescription on a form and handed it over to me asking for me to sign and pay Rs.500/-. I asked him when he will fill the gas, he said that this is their normal company practice that he will hand over the filled complaint with his remark to his technical team who will call next day and I don't have to pay anything to them as the visiting charges is already collected. Next day, I waited in vain till 4:00 PM after which my patience gave way and I called up on the number from which the person had called previous day. There was no response and I messaged him asking what happened to the promise of having my problem attended next day. No reply to message as well. Next day I rang up the number again with same response on third day luckily someone picked up and when I told him what had transpired, he put me on hold and then told me that the technician had tried to call me to fix appointment for visiting but I had not received the call. That was a blatant lie and I told him so...that I have the cell all the time and no missed calls were there. I asked him to take the technician on conference and he stuck to the same line that he had called. I told him that if he keeps lying, I may have to take recourse to law. Immediately the technician said that he will not attend to my call. His manager too took his side and was telling me that perhaps I am not aware what our PM has said in view of the Covid situation and I cannot compell his person. That was 28th June and till date nobody from either the Customer Service Center ( outsourced in Chhatarpur area) nor company Call center has resolved the Refund which I asked. Ofcourse rather than being dependent on a company and its service center which were simply safeguarding their own interest with no intent to serve the customer(I have the exchange with their Customer Care on Messenger & Face Book)., I got the problem rectified by looking up in India Mart and finding a Refrigertor Electrical Shop nearby who attended promptly and charges wise also he was cheaper compared to the quote given by Whirlpool Service center guy.
My Question is since amount involved is paltry Rs.500/- but similarly they have perhaps taken service charges from many ( I could see complaints galore on the Messenger when I posted my resource). How to bring them to book? more