I need a little help Please

Thank you all I am very new to selling on eBay I have been using Turbo Lister. I have a lot of items that I have to use Calculated Postage as some are heavy, over 1 kg. Now this is the tricky bit I send an invoice including the postage, but the buyer wishes to pick the item up for free how do I adjust the invoice to suit so as I do not have to pay the FVF on the postage?

 

Thank You