On the invoice for the item I've bought the address is right but the postage for the postcode came up wrong. I have emailed the seller but no response. Can I initiate the change myself or do they need to do it at their end?

Secondly, I have bought several other things & have tried to pay straight away through Pay Pal but I can't because they make you pay for all items bought together not individually, which of course includes the incorrect postage for one item. Is there any way around this?

Thanks