ebay changed postage

Ebay changed the price I set $8.95 to $13.65

When Previewed the invoice , it showed my price, but after the invoice was sent it showed postage at the higher amount

This is annoying me, the seller. Heaven knows what the buyer is thinking.

You probably updated the postage after adjusting it - this resets it to ebay's calculation, you need to adjust and send, without hitting anything else. just shoot the customer a message and re-send the invoice.