Replacement or repairing of my product not approved despite being in warranty, and provided refund instead

I purchased a bluetooth headphone from amazon of the chevron company in november 2017. Which gave me the 1 year company warranty. The product stopped working and is still in warranty so i sent that product to company for replacement or repairing. But after receiving the product back to company they refunded back my money without my permission. I wanted to get that product repaired or replaced and not to get refund. After refunding i complained them but customer care executive blocked me on whatsapp and disconnected my phone call. So kindly help me to get my product and i will return them the refund they provided me.