Debit note to vendor

I have query regarding whether under GST there is option to the receiver to raise debit note against the invoice raised by the vendor?
If yes then in case if the vendor was unregistered but at the time of raising the debit note the receiver will have to bear the GST amount? so what can be done in this case?
The vendor is not ready to give the credit note against the invoice and payment is also made to the vendor, even when the service is not delivered.