We encountered an error while trying to save the changes. We've made a note of it, and we'll fix the problem as soon as possible.
The SIM card is removable. Push a paperclip into the hole on top, and the card will come out (you may have to apply more force than you'd expect).
You cannot use a SIM card from another provider without unlocking the phone first. Currently, there is no way to use the iPhone on a non-AT&T network. The only way to use it internationally is roaming with a US plan.
Your contributions are licensed under the open source Creative Commons license.