You must wait 4 days and then you can open non payer disputes.

To do this to the right of the item in your sold list is a drop down.

From the drop select Resolve a problem and follow the prompts to open non payer disputes.

Then you need to wait another 4 days and you can close the disputes.

You will get your fees credited back, they will get a strike and be blocked from leaving feedback.

Then you can offer to the next bidders or relist.

Do not leave false +ives for them as that is a breach of policy and if the buyer reports it you will get a sanction from ebay.

Add them to you blocked bidder list Block bidders

And put in place the blocks to stop non payers with strikes.

To put these blocks in place hover your mouse over account in your my eBay page and from the drop down click on Site Preferences then go down the list till you see Buyer requirements and to the right of that click on show then click on edit. From there you can put in place the blocks you want