If it's been more than 4 days since the sale, open a non payment dispute. That gives the buyer another 4 days to pay. If he still doesn't pay, go back and close the case after 4 days (it has to be more than exactly 4 days to the second). You will then get your fees back and the buyer will get a strike on his account. If he gets 2 or more strikes in a year, he will find he can't buy from a lot of sellers.
To open a dispute, go to the item on your selling page and click the dropdown on the right where it says "more actions". Then select "report unpaid item". Then on the next screen you submit the dispute. in 4 days time, go back to the dropdown and select "close case". That will take you back into the resolution centre and show you the transaction. On the right is a dropdown where you select something along the lines of get FVF's back. When you enter the next screen, it will ask you if the buyer has paid or not. If the "no" option is unable to be ticked, the 4 days isn't quite up. Up the top of that screen will give you the earliest time you can close the case.
Once the case is closed, you are free to relist. Just be careful though because phones are very high risk items to be selling on eBay, especially by someone with low feedback. You are a target for scammers. Accept PayPal only (unless it's a pick up, then take cash only). Don't let someone ask for your PayPal email address because they should be able to pay via checkout. Don't let someone overseas ask you to post to someone else (usually their cousin in Nigeria). Don't let someone tell you that you have to provide a tracking number before the funds can be released into your Paypal account. Post with tracking, signature on delivery AND insurance for the full amount paid.
If you have any doubts whatsoever about a buyer, come back here and ask for help. There are a LOT of scammers involved in buying phones.
