Being taken advantage of.

I worked with someone at my current occupation till they tried to cheat the system, got caught and left without handing in any notice or even giving the company the time for an investigating on what he did. It was a certainty that he would have been fired. I had worked an extra day for him. He left before he could return that day to me and as far as the system sees, he worked that day and not me.

I have had a few heated text messages with him and in one he even admits that I worked a day for him and he wouldn't me pay for it and he also admitted he was fired.

I had considered him a friend at the time and I lent him an O2 dongle to help him with looking for work online as in these times, every little bit help. Only he ran me up a massive bill of almost five hundred euros. I recently got that money off him, never in person however, the second time he knew I needed and wanted re-compensation for working that day for him so he sent a buddy of his in to deliver it but he's refusing to pay me the money for working that extra day for him and I seriously need it.

I know where he works and he's just started there as a store manager so there's little chance of me being able to get him fired or get back at him without resorting to violence (that I'm aware of, please correct me if I'm wrong) and going to jail which I can not afford.

Is there anything I can do?

[Edit] I have also considered contacting the company he now works for and informing their head office that he lied on his application form to them. My work colleagues have stated that they will vouch for what I'm saying should I need references. I can't really go into the store he works for and go to the store manager as that's his position so the next one up the food chain would be the regional manager and I have little if any chance of getting into contact with him or her.

Also, everything stated in this post is what happened exactly as it happened so I don't think I could be sued for libel but I am not a lawyer so I'm very unsure of whether or not I should post his name, the company he works for and where he works, as sorely tempted as I am to do so.