Myntra - Myntra refund fraud

This is regarding the anticipation of the amount Rs. *****.** from Myntra to be credited to Citi Bank credit card.
Following is the series of events that happened related to the case.

I ordered * items from Myntra detailed :
Date : **th April ****
Order id : #*********************
Number of items ordered : *
Amount : Rs. *****.**
I returned four out of five items due to the quality issues within the return period stated by Myntra, detailed :
Date : *th May ****
Order id : #*********************
Number of items returned : *
Refunded Amount : Rs. *****.**
I got a confirmation from Myntra on *th May, **** that the refund was successfully processed and added to the Citibank card ****xxxxxxxx****. They asked me to wait till **th May **** for the amount to get reflected in my account.

After the wait period was over and amount was not credited to my account, I raised a dispute with Citi bank detailed :
CITI dispute CaseId : I**********
Provided all the necessary documents for the refund claim.
After following up with Myntra, I got the refund Reference Number : *********** which was denied by the bank saying it's an invalid bank reference number.

Till date I have followed up with Myntra and Citi for countless number of times but have got no solution out of it.
Myntra claims the refund is successfully processed from their end, attached the email.
Citi claims that the amount is not received by them.