I am a private seller selling postage stamps that go in the smallest of envelopes-Why is Ebay charging  only for a large letter when printing off labels e.g Postage to Australia =£3.60 for normal letter whereas Ebay Label for same =£4.50 with no facility to change to small from large envelope-Also Asia and Europe (but latter is almost same Large/small so does not matter quite so much).

This has been for quite a while-Am I missing something to click on? I have spent ages trying to get the smaller letter cost active so I don't think I am.