What should I do about money owed by a "friend"?

I wouldn’t worry about a friend not repaying money I lent to him, but what about services / business work payment?

I’ve had this friend for several years… he moved to another state a couple years ago so I only talk to him scarcely. But he contacted me in the beginning of January and told me he’d pay me a few hundred bucks if I helped him and the company he was working with to handle some technical tasks remotely.

I agreed, being that we’re friends of course. He needed the job done urgently so I went ahead and did the work. It’s been about three weeks and I still haven’t been paid even though it was supposed to happen “right away”. I’ve been getting ignored, blown off and every step of the way has been one excuse after another.

If I don’t get paid, this will surely end the friendship, not because I’m out a few hundred bucks, but because it has exposed the character of my so-called friend. Does he want to throw away a friend for that price? Do I have any recourse to get the money from him or the company he’s working with even though we have no agreement in writing? Should I go “undo” the work I did for them since I’m not getting paid?