Amazon.in - False commitment unethical business behaviour not fulfilling prepaid order

I have ordered "Reebok Men's Club C ** MCC Mt. Fuji/Chalk Tennis Shoes - ** UK/India (**.* EU) (** US)(CM****)" sold by Cloudtail India for a price of Rs. Rs .*,***.** (Inclusive all taxes and delivery charges) on **.**.****. The order was prepaid and I paid the full amount through my card on the **.**.**** successfully. As per the generally accepted principle, I secure the owner right on the product for what I paid in advance.
After the payment on the same day, I got a confirmation email and notification on my registered mobile number and email id with the details of my order estimated delivery date which was **.**.**** from your portal. I was regularly receiving emails and notification alerts regarding my order delivery status from Amazon. I had checked the delivery status on the **.**.**** (Estimated Delivery Date) in the afternoon, till that time I didn't get any information regarding the unavailability of stock. After some time I rechecked the delivery status and found it was not out for the delivery and for the details of the same I made a query through Amazon customer care services.
After the query, I got an email stating that the ordered product is out of stock and the delivery will be delayed and the estimated delivery date can not be provided for the same. I don't understand if the stock was not in hand so why Amazon mandate to pay for it in advance? I got the information after the query raised by me for the delivery status on the estimated delivery date, its Amazon responsibility to provide timely and accurate information to the consumer for the status of his order?
I've mailed to Amazon regarding this issue. I clearly mentioned that please do not ask me to cancel my order or refund me the amount. I paid for the product but you cancelled it without my approval, is it an ethical business practice?
We trust Amazon that's why we use it for online shopping but Amazon has no time to resolve customer queries even they won't reply to our emails timely. When I got an email for nonavailability of stock, I felt really bad. After this, I called customer care executive Mr Samrath (Senior Customer Executive) but it was a pathetic experience for me. I asked him to resolve this matter then he told me that we can not help you in this matter. I asked him then where should I go for the redressal of this issue but he didn't provide any information on this.
After this, on the same day, I emailed Amazon regarding this issue with all the relevant details and request to solve this issue. I mentioned all the aspects clearly and I also mentioned that "Please do not pressurize me to cancel my order and take refund because this is not what I paid for. I paid for that product and I want it as simple as that." But I didn't get any support from Amazon side even my order has been cancelled and refund initiated by them without asking for the approval to do that from me. I have all the relevant documents and images.