Cancel an invoice?
Is it possible to cancel an invoice that I have already approved and sent to the client? The situation is as follows: a travel agent booked a room for a customer for two nights and I sent the invoice (not yet due). A month later they changed the booking to three nights. I sent a new invoice for the extra night. Now they inform me that they want only one invoice for a total of three nights. So I need to cancel the two invoices already sent (2 nights & 1 night) and send another invoice for 3 nights. What do I do? Can they and we just delete the invoices even though it's already approved and sent? Thanks for your help