Amazon.in - Refund not issued on regular basis

I have placed a order on amazon for yonex voltric force
Order no.***-*******-******* upon receiving the product was identified as different from what was ordered and amazon.in accepted my replacement request and gave me a replacement for the product when they received the wrong product in the warehouse and it took them **-** days to give a replacement(order no. ***-*******-*******) that too on regularly emailing them, now the product received this time was correct but had some quality issues so I raise the issue and they agree to give me refund on successful return of original item delivered .
Now the catch is that they place a pickup for order which I received first and upon receiving they mail me that the item has been received and your replacement is now complete but I have returned the replacement itself which I have received the second time.
I returned the original item with return tracking no.************ I have mailed them twice and called them thrice for the issue and they keep on telling reasons, I want to get my refund as the product is returned to them in original condition.
Note: I have all proofs of audio recording and mail conversation with them.