Zomato — refund of cancelled order I placed by mistake

Address:

Netaji Nagar, 1st by lane,, Keshabganj Chatti, 713104

I've placed an order on Zomato by mistake and immediately I cancelled it.
But they didn't refund my money back. They are saying there is penalty charge. But I cancelled as Soon as possible. How they can say such words?
And penalty should be some amount of the order price. They are saying penalty charge is full of the amount of order.

Please refund my money back.