Answers: Sure you can, and it's never been easier for any cell phone. I enjoy an iPhone unlock with the use of tremendously simple software and now I use T-mobile. And the sim card is effortless to access, it is right on top of the phone, beside just a paperclip you can catch to it.no bcuz you can't even take out the mobile let alone a sim card. so no. unless you hack it. but probably at hand s not.
you have to use the one explicitly provided by them unless you do a hack and I do not recomend you doing one because if you brick your iPhone you void your warranty.