iPhone: once unlocked, always unlocked?

Question

I got an iPhone from a telco carrier two years ago, as at that time, I didn't really know whether I bought the phone unlocked or was it locked to that specific carrier.

All I knew was, I change my telco afterwards, and I could use the new telco's data plan and voice and SMS service without trouble.

As I want to travel to overseas soon, I am looking forward to buy local 3G SimCards to satisfy my appetite for Internet surfing. I wonder whether I can do so without performing extra steps on my iPhone?

I think when I managed to change from one carrier to another previously, it indicated the phone was unlocked, at least among local carrier, but I am unsure whether this phone will remain unlocked when I travel overseas? Or is there a possibility that although you can change local carrier, but for you to change to an oversea carrier you would need to do some other steps?

Answer 1

SIM Unlocked means SIM unlocked. There is no lock, so you're free to go.

Answer 2

if you where able to use another carrier locally or not, with a different SIM card, you are basically good to go, however if you didn't change your simcard, and simply used another carriers antennas, it proves nothing! so you need to test your iPhone with a new simcard, from a different carrier, different data plans doesn't matter!

second depending on the country you are traveling too you need to check to see if your phone can handle the different bandwidths that are used around the world, if you want me to help you, you need to tell me your phone model, and the country witch you are traveling too!

and you said you bought the phone 2 years ago, most likely you will be able to call your carrier and have them unlock it for you, perhaps for a small fee!