What happens when you do change your address? For example, although I have a house, I had some of my items addressed to a non-existent "Department 300" at the house address?
To end the Unpaid Item demands you can either try again to pay or contact the seller and ask her to end it. Since she is being charged about 20% of the price and shipping on the item as her fees, this is unlikely.
You could also offer to send her a postal money order.
If you do not pay, however, you will get a Strike. Since most sellers have automatic Blocks against bidders with Strikes this will make it very difficult to buy on eBay.
