Mahindra Finance — fd effective 2 days later than the actual payment date whereas banks to give effect instantly

I had booked an FD in September 2019 and made the payment through Internet banking and my bank account was immediately debited on Friday itself but the company made the FD effective from Monday (not specifying dates, amounts and FD number for security reasons nor willing to attach any pictures of the FD or bank account screenshot)
When I followed up with the company the customer care people said that it was their policy to start the fixed deposit account from the next working day.Thus is absurd since all other companies including the scheduled banks give effect to the FDs as soon as the amount remitted is credited to the companies account.I told them that that means they are using our funds for 2 days by not giving any benefit to the customers.How can any company not pay interest to us for 2 days when the amount was received by the company 2 days in advance of a working day.We pay online and get instant credit-see the case of all public and private sector banks, Bajaj finance, TATA capital, and other renowned companies.
Kindly take action against the company for using public money and not giving due benefit to the customers