I had a customer with the username Omar Parvaiz who refused to send payment after I had posted the essential oil articles on his blog. All the articles are here on his site http://www.talkoils.com/category/essential-oils/.
Sadly as it was a content writing task, there is very less you can do here. You should have asked for advance payment when the task was assigned to you. Also mention the exact user name URL so that other members here can be aware.
Do you have any solid proof to sustain your accusation? @seo_buzz is right, you should've asked for payment in advance. Sorry for your loss.