Amazon India — Sudden cancellation of a product delivery after debiting the amount 6 days ago

Address:	Kolkata, West Bengal, 700019
Website:	www.amazon.in

5th March I placed an order for Netgear Router, Order ID[protected], for which I made a payment of Rs 3100 through my credit card.
I got a confirmation from Amazon on the delivery date between 12th- 17th March.

I had also sent a mail to HANHIL Technologies from Amazon website for a quicker delivery, to which I got a receipt confirmation.

After 6 days Amazon has sent a mail on cancellation of the order without stating a reason.

I called on helpline to which a person called Mayukh informed that the product is out of stock. That day, that time it was appearing as available, so I could make the payment.

My mother (60 years) stays by herself and is dependent on wifi connection for communication with relatives and friends.
I'm a single working lady with 6 working days, not possible for me to visit the market to purchase.

Kindly help me resolve the matter and get the product delivered to our address.