India Post — parcel held by customs for unspecified reason

Tracking id# RB[protected]SG.

Parcel from ali express Singapore has been arrived to India Post, Mumbai long back. But whenever I track the same it's showing ''Held by customs for unspecified reason'' since 28th January 2019. Not yet get any call / intimation from either India Post or Customs. But got a Spam call from an unknown person(I have his number) asking for money to release the parcel. He even shared his bank account details with me to send the money. More scary is he has the parcel with him. He sent the picture of the parcel to me on whatsapp.
Please have a look and release and deliver the same asap.
P.s.: picture of the parcel attached which was sent by that person.