@kittylun what is the current status of the report? Also, is your home country Singapore or Hong Kong?
If the report shows Sent for Payment, Processing Payment or Paid, you will not be able to make any changes. If it says Submitted & Pending Approval, Approved & In Accounting review, you should be able to recall the report.
To recall the report, from the SAP Concur home screen, click Expense at the top. You should see the report on the next screen that opens. Just click on the report tile to open it.