Zomato - Refund is not full and the partial refund is not credited to my card

I've received my order from Zomato in an absolutely filthy condition. The smell spread across the room as soon as I opened the package. I contacted the customer care and as soon as I sent the picture I got only one option to accept the refund. Why do we order on the app in the first place? Isn't it trust? The refund is not even full. I've paid *** and got ***, that too in the form of a promo my next order. Didn't want to accept that. But they did not even give me another option there. But to select the promo refund.
I also mentioned in the chat I want my refund back to my card and I told them I want the complete ***. The customer support says that the ** rupees were deducted as part of the delivery charges. The delivery charges on the order were ** and not **. So how can they even charge ** for delivery?
It's not about my ** rupees. How many **s like this are being looted every day? I want to put an end to this. Please help.