Eway bill

Dear All, 

I have a query w.r.t eWay Bill, details of which are given below.....

eg : If we sold goods from Delhi to Mumbai & generate eWay bill. 

      After the delivery of goods to customer found a mistake in Invoice & customer rejects to accept the said invoice.

      now customer want to revise the invoice with correct detail. 

    Here... Our system not allowed correction in invoice. Hence we are showing it as a sales return & genrating a New invoice as        per customer demand.

   Now my Qns is that.....

    because Material has already been delivered against earlier invoice.... against new invoice should i mentioned a new eWay bill or earlier eWay bill remain valid ????

Thanks in Advance..