Amazon India — Deliveries delayed after becoming prime

I joined Amazon prime hoping that I will get faster deliveries.
Strangely all my orders are processed as non prime member even though the seller item qualifies for prime delivery.

On day of delivery the item reaches the final delivery hub at around 7 AM in the morning. Normally it should be out for delivery by 11 Am.
But it just does not go out for delivery and in the end returns to the previous hub on its own without even getting out for delivery.
This is consistently happening.
I am getting all my deliveries as non prime member despite being prime.
Amazon prime is a waste of money.