Amazon India — amazon is not refunding my funds and neither they are doing a return pick up

Address:

Hyderabad, Andhra Pradesh, 500018

Hi team,
First issuer:
Amazon india is selling the malabar gold ornaments. I bought a gold pendant of 1.52 grams and seller sent only 0.82 grams gold pendant.
Is the weight is almost half, i wanted to return it. Seller states its amazon's responsibility for a reverse pick up and amazon states its a seller responsibility, since it is a third party seller.
Now both of them are denying for a reverse pick up and as it is a gold item. I don't want to send my self via private courier as there is a possibility of theft and mishandling of it.
Second issue:
I bought this pendant when there was an offer running. The original price of the product is 6313rs. But if i purchase item worth 5000rs. I was entitled to receive 10% instant discount and also 1000rs amazonpay cash balance. So after applying the discount i got this item for 5681rs.
As seller sent only partial qty. He refunded 2531rs but i received only 1331 rs in my bank account. Now because of sellers mistake amazon deducted 1000rs which they gave an offer amount and bank deducted discount of 200rs. As partial qty is not eligible for amazonpay offer. I ended up receiving on 1331rs in my bank account.

I want to return the product as i haven't received what was shown on the website, but no one is taking the responsibility of the return.

Please help.