Fraud and cheating

A fraud has been committed by Air Vistara airlines.
My Booking ref# KL85BJ (Delhi- Mumbai Flight)
I had pre paid Rs 1000 for seats 7A, 7B & 7C.
I was travelling with my parents who are senior citizens and hence I had chosen front seats (that I could afford) for their convenience and had promptly paid for those seats.
But during check-in, I was shocked to know that I Can't be accommodated to my choice seats.
And instead can't sit together with my parents during the journey. This is utter fraud. If I have paid for a seat then I will expect that seat no matter what. This is the rule of any transaction. I did have a word with their staffs and lodged a complaint (Complain# TCT202012063030174) but they didn't resolve my issue instead they told me that someone at the airport counter will resolve my issue. With this hope I went to the airport with my parents. My father is wheelchair bound but they did not pay heed to any of it.
At Delhi Airport, despite haggling with Vistara staff ( namely Ajay and Priyanka)at the Delhi airport counter they duped me into checking in with randomly assigned seat with a promise that our tickets will be upgraded. After more than an hour and seeing the plight of my elder parents I succumbed and took a chance and trusted Vistara airlines, hoping that we might be assigned seat to the convenience of my elderly parents. I even waited for 15 minutes at the door of the aircraft with my parents but to no avail.
To add insult to injury, ( my mother who is severely diabetic) , I had chosen veg meal for diabetics while booking the tickets, but all she was served was a cookie and potato sandwich!!! Had I known this, I would have got something for her from home. Moreover, this was their first trip post covid and they were really scared and hence I was with them to give keep company and usher them to Mumbai with safety. But because of Vistara's incompetence and unprofessionalism, they had to sit with strangers in the middle seat despite paying for our choice seat. They might as well had come on their own.
They were really disturbed and scared.
Adding insult to injury was at Mumbai airport when no one from the airlines attended to my father with wheelchair (despite putting a request while booking and reminding the cabin crew).
My parents were harassed. Air Vistara has indulged in unfair practise and they need to be severely punished and should be thought a lesson so that no senior citizens/passengers like my parents be harassed in future. Their tall claims of the wonderful customer service need to be exposed.
I have tried to reach out to them but they haven't responded to any of my mails. It will be a befitting if this forum takes stern action against this airlines.
Looking forward to your response and guidance.
Warm regards
Nishant Lal