Material Not Dispatched with Eway Bill

Experts,

A firm had dispatched the items
worth Rs 10 lakh to the inter state customer with bill along the waybill and the item has arrived.

That firm found out a few days later that 2 lakh of it was missing without sending a valuable item.

Now how to send the missing item with e-waybill?

Note:
It is not possible to get a debit note as the customer is a government company.


Pl suggest