Certification of payment amount

Being a contractor Worked for one client. according to the po.they suppose to release the advance amount for supply and installation of the material. Due to delay from their side, even though we supplied the material which was not sufficient. Later they started supplying material instead releasing the advance amount. Purchase invoice was in their name. In final Total billing amount 42,16,594.76 ( excluding GST )nTotal material purchased 27,27,141.66 ( Excluding tax by the client)nnDebit is as followed:nnTotal Amount - 42,16,594.76 ( Excluding Tax )n (-) 32,93,492.87 ( Including GST )nnBalance - 923101.13nnnAnd other debits are also was there which was ok. Now my question is if invoice is in their name and they are getting ITC from the government. They are not suppose to debit from me. If they are debiting from me it suppose to be debited from (final amount + GST ). Need help on this. Advance thanks for the help.