India Post — I have received oil written interview call letter after interview date

Address:

Karbi Anglong, Assam, 782480

Dear, sir/madam
I was unable to attend the Oil India Limited, interview held on 18th &19 march 2017 due to late delivery of written exam calling letter to me. It was sed via speed post on 8th march from Dibrugargh to Bokajan and i recived on 22nd march. I just want to know Why such thing happened? .
Pleas take necessary action.

With regrate.