Sometime there is no other ways to unlock a phone. We have a Sim-Free iPhone 7 bought from Best Buy. It's locked to the first carrier sim you insert into it. At the time not many people know this would happen including the people at Best Buy. You could search "best buy sim-free iphone" and you will find lots of people complaining about it. It is purchased with full price but locked to T-mobile. T-mobile won't unlock it because it was not purchased directly from them and they don't have the IMEI number on their inventory system. Apple won't unlock it because it was locked to T-mobile and they need T-mobile to tell them it is okay to unlock. Best Buy can't unlock it because, well they are not a carrier and they don't unlock phones. Everyone agrees that it was purchased full price paid as a Sim-Free phone but now it is locked to T-mobile and no legitimated place could unlock it.

So if the "scambags" could unlock it, more power to them. Personally, I think carriers who locked you phone when your phone is paid off are the scambags. That's one of the reasons I wanted to switch to Verizon. Verizon does not lock your phone even if it not paid off. As I understand, any LTE phones on Verizon came unlocked as you bought it even on EDGE payment plan.