Amazon India — I have not received the refund by amazon nd bank is also not helping

On 21st april i have cancelled my amazon prime and they have told that i will get refund on 26th april but on 28th april i have seen but i have not got my refund when i have talked with amazon custom care they are telling that refund has already been processed but i have not recieved the refund and bank is also not helping they have given a reference no-[protected] told to contact customer care of your bank but when i am dialling customer care it is showing invalid no so i request you to make my refund as soon as possible