Hi KH Fong,
So far as I know, there is no existing report can be used to update billing status in this case.
If you need to change table content directly, you can try following steps:
1,SE16->VBRK->invoice number->execute
2,double click on the entry
3,/h->enter->enter
4,in debugging mode, change 'code' to 'EDIT'-> execute(F8)
5, Then you can see the table content is editable, you can change posting status to C by yourself.
Please test well in your test system before you perform the same in your production system.
I hope this helps.
Best regards,
Tao