Amazon India — Didn't get my refund of the phone I ordered and cancelled

I have ordered iqoo z7 from Amazon on 23 may after 4 on 27 it was not dispatched and I need it immediately so I cancelled the order then I waited for 5 days to get my refund but received nothing then I contacted customer care and they said they will raise a ticket and give me a rrn no. Which I have to give to my bank and get the refund as they have already given the refund then I waited for 5 days but again I didn't receive the no. Then again I go to the customer care and they again told me that they will raise a ticket and give me the rrn no. And told me to wait twice today is 14 June and I haven't got the refund or rrn no. The amount isbRs 19, 999 which is not a small amount. It is unexpected from a big company like Amazon. I can't wait more now plss give the refund asap.