Amazon India — Order#[protected]delivery issue

Address:	Pune, Maharashtra, 411007
Website:	Amazon.in

I have ordered apple iphone 7 plus (Rose gold, 128gb) from amazon.in to gift for my beloved on her birthday. I availed benefit of 1day delivery but paying rs.100 extra and my expected guaranteed delivery date was 12th may, 2017.
But it was not been delivered yet and still showing as in-transit. And my expected delivery date was changed to 15th may, 2017.
I have contacted many times to customer care for the issue and everyone promised me that my product will be delivered in next 24hrs.
It's been more than 6 days and now amazon cs department were telling that my product has been lost in transit and offering me refund for the product. (If i wanted only refund i would have cancelled it right away when product was not delivered at very first instance).
These kind of delivery issues were pretty usually happen with amazon.
Kindly someone look unto this issue and help me in getting my product at the earliest.