You are talking about "friend" list as it is LEGIT. If I wouldn't change my friend list (I have to approve), I'd have randoms in my "friend" list. Goddess was a staffer for a short period of time, anyway. To the main subject.
At beginning you said you have it done, working - obviously a lie. If you don't want to refund, simply send him what he paid for.
You could simply mention about that. You simply said "gimme 50e" out of the box. Anyway, if that's true what you say, then yea, let's say it's legit.
You didn't even answer him about the progress. Ofc, daily spam on the Skype is annoying, but that doesn't mean you have to ignore your customer.
It's simple. Give him what he paid for, else refund half (decide the amount on your own) of the money. Else, banhammer.