[Resolved]  Whirlpool India — Refrigerator service charge mismatch

Hello,
I have been a loyal customer of Whirlpool for the past decade and today perhaps was the worst experience that I have to endure so far. My refrigerator (WHIRLPOOL NEO FR278 ROY PLUS-35/262Ltr REF-WINE REGALIA) bought on 28th July 2016, had recently started having cooling issues and as a result, I lodged a service request online (number:[protected]. A person attended to the request on 20th June 2020 and charged me 413 INR (ID no on bill: KOL[protected]). He suggested that I had a gas leak from the refrigerator and will send someone to repair it. Today (22nd June 2020), a person from Mondal Refrigerator Co (authorised service franchisee from Whirlpool, 81/K A.K Mukherjee Road, Kolkata 700090) came and attended to the call. He repaired the leak and also changed a spare part. He charged 2500 INR for the same. Now I have the following questions:
First, when I asked him to adjust 413 INR (for the previous visit) with the current amount, he said that he can't do that as it is not the policy of whirlpool. Although, from my experience at resolving service requests with several other companies, you usually get the amount that was charged during the initial inspection adjusted with your final bill. I want to know why I couldn't avail the same request. Second, in the bill attached, he has mentioned two items that were repaired or attended to. The first was the copper filter drier that was changed and he also did a gas refill for my fridge. The refill came with 170gm bottles (from Godrej) and he said that he has refilled only 100gms for my refrigerator. Now the gas canister was priced at approx 250 INR in most websites online and the spare part (the copper filter drier) was charged at 10 INR each a piece. He replaced one only.
So my question is, why was I charged 2500 INR for the repairs and also why the 413 INR that was not adjusted? And second, I want a price-wise description of the repairs done or the product replaced. Please note that I am not asking for a refund. All I am asking is you provide the part-wise breakup of the bill and not just provide the same in a lump-sum format. I hope this will get resolved soon. Whirlpool has always been my first choice.