Hi Ankish,
As mentioned by Kalyan above (check suggestions from SAP in his comment), you should use the interface Collective Payment Order Notification given by SAP in ESR (Enterprise Service Repository) SAP APPL (SAP APPL 6.05). If your PI environment doesnot have it then you need to request yuor basis to download this from SAP.
After you download the ESR , you can find the standard Service interface called "CollectivePaymentOrderNotification_In" under Namespace http://sap.com/xi/APPL/Global2 .
Now once you have this interface downloaded, create a new message mapping using the message Type "CollectivePaymentOrderNotification_async" as Target, and your message from BANK or SWIFT (uploaded into PI as external definition) as source. Map the required fields , mainly map the external status code from BANK to ExecutionStatusCode field. Also map the required header fields.
Once you create the new mapping , create required Integration builder objects and you are all set.
The CollectivePaymentOrderNotification interface is proxy in ECC which has required methods to update the BCM with the status.
Also please check below links for more information.
http://help.sap.com/esoa_erp2005_ehp2/helpdata/en/46/802b59e186429ee10000000a1553f7/content.htm
Regards,
Suresh