Amazon India - Wrong Product Delivered

I ordered a Battery Operated Car on **th September **** for my baby boy's first birthday. As per product brochure the shipping weight of the car is about **kgs and we received a small parcel having weight of **grams through Indian Post on **th October ****. My parents in laws thought it would be a different courier but when we cross matched with order and tracking number it was the same which is we ordered a car. We were shocked and realised something happened while dispatching the product and we contacted Amazon customer care and provided images and asked for replacement or refund which is easier for us. They promised a refund will be done within a week. We made a follow up after a week about our refund. They checked and confirmed it's processed and will be refunded within a week and it is about complete one month today they confirmed the refund can't be done because the product already delivered on *th October ****. But we received the wrong product. If anyone has sense they can understand easily how it is possible **kg of car will be delivered by ** grams of parcel. Here I am enclosing all the documents and images for your reference. Please look into this matter and resolve my issue.