not refunding my money 35999 rs.

i placed an order for oneplus 6t on 1st nov. 2018 with order id ORDER # 408-6685129-4177143 and i recd. a defective product which i returned and amazon confirmed they recd. it back on 16th nov. 2018 and for which they gave me a replacement product with ORDER # 408-5078805-7753169 which i cancelled on 12th nov. 2018, i refused the replacement even before it was shipped and the replacement was returned to seller and since that day i’ve been calling amazon customer service for the refund and they always give me a 24 hour or 48 hour period to wait and promise me that i’ll get the refund confirmation in 24 to 48 hours but till date 23rs nov. i have not recd. any official confirmation from them about the refund. I have talked to them hundreds of times and they have promised me million times to privide the refund. All they say is this amount is big so we have to get approval for this from senior so kindly wait for another 24 hours we will call you back and blah blah but no luck 4 me. kindly help me plz. to get my money back.