All recent iPhones contain a SIM (subscribe identity module) card slot on the right edge of the phone. A SIM card stores the information your device requires to connect to its network and access voice and data services provided by your carrier.
There are a couple situations where you might need to swap the SIM card in your iPhone. If you upgrade to a new phone you will need to move your old SIM card into your new phone. While traveling, you may want to swap out your SIM card for a local SIM to avoid roaming charges. If your SIM card malfunctions, you may need to remove it and replace it.
Luckily for you, it's really easy to remove your SIM card and only requires an Apple SIM-card eject tool or a regular paper clip.
The only required tool for removing your SIM card is an Apple SIM-card eject tool or a plain old paper clip. If you go the paper clip route, you'll want to straighten the long end until you have at least a one-inch long straight piece.
Other objects may fit into the SIM tray opening, just make sure the object easily fits in the hole and doesn't mangle the SIM tray hole or leave any unsightly marks on your phone.
Nearly every iPhone has a SIM card tray. The only exception being the CDMA model of the iPhone 4 (Verizon, Sprint). Older model iPhones have the SIM tray on the top while newer models contain it on the right side. Check below for specific models: