Punjab National Bank [PNB] — Amount not credited

I purchased Alexa echo from Amazon on 13th Nov for which 5000₹ was debited from my PNB account. Later I returned the product for which Amazon issued refund on 18th Nov. but till now no amount has been credited to me. Amazon has provided me with the reference Id as well as transaction Id.
When I call bank customer care and spoke to them about the same they simply said that I’ll have to wait for the amount. I asked them about the dispute form they told me that no such form exist and they can’t help me with the same.