Cannot seem to find the option for revised invoice in the my ebay drop down list or the sold item drop down list.

[0408astrolec]

I have sent an invoice which when pre-viewed showed the total amount including postage but the buyer only got invoiced for the cost of the item, I need to send an amended invoice but cannot seem to find the option in the my-ebay drop down list or even in the options list on the sold item. Any ideas where I can find the option or how I can send a revised invoice.