The combined shipping costs must be made into a single invoice to get the lower combined rates,
so don't pay before requesting a new invoice.
In order to comply with the newer eBay rules on adding tracking information -
items once paid for must have tracking entered by the shipping date deadlines (2 days).
If you make payment before requesting an updated invoice with the correct postage, I will assume you do
not have further purchases and will send out the item alone, neither can I correct it.
I always use tracking with the items, so it is why the shipping price is a little higher since
the only way is to send it is either Media, Ground Advantage, or Priority rates to ensure that they get there.
Media items and non-media must be combined at the regular rates for
the non-media rate, so may not be as cheap as sending separately.
Payment is required within 3 days, unless arrangements have been made with seller,
and should payment not be made; eBay has a program that cancels the order after 4 days of non-payment