all my custom order listings have had their everywhere else prices changed to match my domestic prices resulting in people not being charged the right amount
and even listings where the price still shows as what it should be, when purchased they are being charged at the domestic amount too
Do you mean your regular listings or a custom listing for a particular customer? Could you not just add the correct postage as flat/fixed rate in that instance? If you use shipping profile double check those. Sometimes they glitch. Try deleting and readding the profile in your profiles area then deleting and readding to the listing and see if it fixes it.
I mean they have charged the domestic rate for an international order. This has nothing to do with postage