Delhivery — They lost my shipment

Delhivery guys picked up my shipments- two big bags full of books, both of almost 10 kgs.
They picked up the shipment on 30 April.
on 1st May, those bags were tracked to be in Bangalore Facility.
and after that, there was no update on those two shipments. I raised multiple tickets. And almost after a month, they took action on one bag and delivered it.
And, for the second bag, they simply marked it as lost on their website.
It was a big bag, not a small package that can be lost just like that.
Also, it never ever came out of Bangalore. Within 1 day they lost a big bag full of my hard-earned books.
I am so disappointed because those books were so precious to me.
Delhivery doesn't even have any phone support system only a ticket system. They assign a single person for the ticket and I believe the person who is handling my ticket "Priyanka Sachdeva" she has not taken any action on the ticket.