How do you go when they make one payment, but include both postage costs?

I just refund. And it is easy enough in C&S to put both items on the one transaction, which in turn, adds the tracking number to both items. As does usingthe eBay labelling system. i don't know how it goes for large multiples, though. Given the records C&S keep it would be easy enough to show that both items were sent in the one parcel.