I had an iPhone locked to AT&T USA. Gsmliberty.net offered an unlock for my iPhone for 75 Euros. It was cheaper than others, where I would only find an unlock solution for 150-200 dollars. I read other reviews that said they are trustful, but they never said anything about an iPhone 4 and especially one locked in AT&T. But, since I was able to talk to somebody I said that if they won't do anything I will be able to get my money back if they can't help me.
So I payed and waited. The only thing that I complain is the fact that they promised an unlock solution between 1-3 days. It took like 9 days, counting the weekend too. I did write them once and asked what is taking so long and the responded that they apologized and that they know but hope to find the solution by the end of the day. Well it took another 3 days, but in the end it was worth it. I didn't mind the wait, I was just scared of a scam. But in the end they kept their promise and now I have a permanent unlocked iPhone. So thank you GSM Liberty!