I tried Cellunlocker.net after upgrading my 4-year-old iPhone 6's battery, to have the option of having a smaller phone in my pocket when I didn't want to carry around my current plus-sized one. Also, having an otherwise functioning iPhone cosplaying as an iPod Touch seemed a bit wasteful...
The 6 was locked to SoftBank in Japan, and Cellunlocker.net came back to me in 7 days. The unlocking instructions went smoothly.
I needed to download the .mobileconfig file from the website of my cheap SIM's website just like I'd done with my main iPhone, and that went smoothly too. (I actually emailed it to myself to have a copy stored on the device in case anything came up and I wound up with no data connection.)
I can now swap my cheap SIM into the now-unlocked iPhone 6 when needed. Very happy.
Bottom Line: Yes, I would recommend this to a friend
