Biba — Not receiving Bill from BIBA Cannaught Place New delhi

We had taken from Store of BIBA at Cannaught Place Delhi, a fresh peice kurti, We did not receive the bill on whatsapp as the no was deactivated . We called the store multiple times but the Bill no, neither the Bill screenshop was shared with us.

Now we want to return the product and exchange it, we have no clue on how to proceed .
very very disappointed.