To do so, hold down the Power button until :slide to power off" appears at the top of the screen and then slide the switch at the top of the screen to the right.


The Power button is on the top of the right side of most iPhones, though you'll find it on the very top if you're using an iPhone 5 or older.;
, SIM cards have gotten smaller over the years, and older iPhones may not support newer SIM cards (and vice versa). Make sure that your SIM card will fit in the iPhone you are using.


iPhone 5 and up use a Nano SIM (12.3mm x 8.8mm).
iPhone 4 and 4S use a Micro SIM (15mm x 12mm).
iPhone 3G, 3GS, and original use a Standard SIM (25mm x 15mm).
 For most iPhones, the SIM card tray is located along the right side of the iPhone, about halfway down.iPhone 3G, 3GS, and original have SIM card slots along the top of the iPhone.
Every iPhone model except the iPhone 4 CDMA (A1349 Verizon/Sprint) has a SIM card slot.
 Many phones come with a SIM eject tool, which is a tool with a small pointy end that allows you to release the SIM tray. If you don't have this tool anymore, you can straighten a paperclip instead.
 With a little force, the SIM tray should pop out a little bit.
 Do so gently, since both the SIM card and its tray are fragile.
 Because of the indentation on the card, you should only be able to place the new card in the tray in one way. If you aren't sure, just insert it the same way the original card was, with the gold contacts facing down.
 The tray will only insert one way.


Make sure the tray is all the way back in the iPhone before continuing.
 Doing so will turn your iPhone back on. Your iPhone should connect to its new network automatically, though you may first be prompted to activate it.
 Depending on your carrier's data plan, you may not see the activation prompt until you connect to Wi-Fi., If your iPhone isn't activating over Wi-Fi, using a computer with internet access may invoke the activation process. To do so:


Plug your iPhone into your computer using the USB charging cable. If it doesn't automatically launch, open iTunes.
Wait for iTunes to activate your SIM for you.
 In the event that your iPhone simply won't recognize the SIM card, restoring your iPhone may prompt the SIM to activate upon restarting.
 Provided your phone still won't activate the new SIM card, calling your carrier (e.g., AT&T, Verizon, or Sprint) may be your only option. Once they verify your account ownership, you'll be able to ask your carrier about the new SIM; if the problem isn't simple enough to diagnose over the phone, you'll probably have to take your phone into a carrier store to have it examined or set up for you.
Power down your iPhone.
Make sure the SIM card is the right size for you phone.
Locate the SIM card slot on the side of your iPhone.
Find your SIM eject tool or straighten a small paperclip.
Push the tool or paperclip into the small hole next to the SIM slot.
Pull the SIM tray out of the iPhone.
Remove the old SIM card and place your new SIM card in the tray.
Slide the tray back into the iPhone.
Hold down the Power button.
Connect to a wireless network.
Connect your iPhone to iTunes on a computer.
Restore your iPhone.
Call your carrier from another phone.
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