Delhivery — Delivery of parcel delayed indefinitely

Booked a courier on 17th April, pickup was supposed to be on 18th and delivery on 21. Then the parcel wasn't picked up till 20th. And the delivery executive assigned was mumbling on the phone and non stop calling me even though he dint know anything about the pickup of the parcel. Tried getting in touch with Delhivery via multiple complaints, only get one response in the beginning and then they ignored all other issues raised. Then they kept extending the.parcel.delivery date. First it was 24, then 26 then 27 now 28. I still haven't received the parcel. Their website says 2-4 days. Its been over 10 days. I have couriered a very expensive article. They have no idea where the parcel is or when it will be delivered. All they keep replying is sorry for the inconvenience, we will try to deliver at the earliest! I needed the aprcel urgently but they have really been extremely incompetent.