Reliance Trends — Didn't send me any e-bill therefore I Couldn't exchange

I have purchased a dress from trendz on 08/11/2020 from trendz, diamond plaza, kolkata. I didn’t get any e-bill. My purse was stolen after somedays. Therefore i dont have the physical bill. I wanted to change an item on 2nd December, 2020. But the people from trendz told me that they dont have any database and i Don't get any ebill. In this covid situation everybody sends ebill. They didn’t allow me to talk to the manager. Please look into this matter. Otherwise i will go to consumer forum.