Myntra.com — not providing invoice copy of my product

I purchased boat headphone from myntra.com on 22dec. Headphone stopped working after 4 months, for warranty claim, i called customer care around 20 to 30 times but each time they played bluff by saying we have sent an invoice to your mail-id but non of time i got. As per my understanding myntra sells old products on their platform because of that for warranty claim products they are not sharing the invoice to customers.

My registered mail id on myntra a/c : [protected]@gmail.com
Order no:[protected]-1662101
Mob [protected]