I spoke with a representative beforehand because there is a concern that it might not work if the phone was unlocked previously. It turned out that my phone, the T-Mobile HTC MyTouch 4G does not have an issue with this. I had a little difficulty using the online form, so the service rep handled it for me. The unlock code came in an hour. All went well. The representative was very helpful. Yes, I would recommend Cellunlocker.