Thanks Christian for suggesting delta upload from ISU to CRM. The request load did update the dates correctly in the backend CRM GUI i.e., when you view the transaction via CRMD_ORDER Item->Service Data, we can see the updated time slice with contract end dates for old product. However the same updated info does not reflect on the Fact Sheet for the BP. The snapshot still shows the same dates as mentioned above.
Secondly I would also like to know if the Contract item system status shows "contains errors", how do we go about debugging these errors?