DTDC — Blackmailing me for more money to return product (DTDC)

Address:

New Delhi, Delhi, 110062

I am a jewellery company and was running a contest. DTDC took my package for delivery, an i-phone first prize.
We mentioned the exact price on the package and even told the delivery guy. He said no problem

They didn't deliver it for 3 weeks. The tracking number showed no progress of the package. On continuos chasing, they were able to locate and now asking 1500 for returning it.

They are harassing and blackmailing. Instead of paying fine themselves for the loss we had to face, they are asking for penalty.
They holding our product as leverage