Volume Up and Volume Down Buttons
Directly below the Ring/Silent switch is a pair of volume buttons. Press the plus button (+) to increase volume and the minus button () to decrease volume. (In the Camera app, the plus button also functions as a physical camera shutter button.) In the Settings app, you can choose whether these buttons affect only noises from an app, or whether they control systemwide sounds as well.
SIM Card Slot
The iPhone can operate on multiple cellular bands, thanks to its dynamically switching on-board radio: various bands of the LTE cellular data standard, HSPA+, DC-HSDPA, GPRS, EDGE, CDMA-EvDO, and HSPA. Major U.S. partners for the iPhone include AT&T, Sprint, Verizon, and T-Mobile.
When you purchase a new iPhone, you can do so in one of two ways: with a cellular carrier contract or contract-free. The first option lets you receive a significant discount on the phone, but you have to use your iPhone solely with that carrier for two to three years, depending on your carrier and region. Contract-free phones allow you to use any carrier's pay-as-you-go plan but are several hundred dollars more expensive up front. Either way, you'll need a carrier to talk on your iPhone and use cellular data.
Your iPhone needs a nano-SIM card to connect to a cellular provider. Without it, you won't be able to access call networks or cellular Internet, only Wi-Fi. If you sign up for a contract when you purchase your device, this SIM card comes preinstalled; if you don't have a contract, however, you need to pick up a nano-SIM from a supported cellular carrier. You can see Apple's full list of supported spectrum bands on Apple's iPhone webpage.
If you have a contract-free phone and need to install a nano-SIM — or you need to access your current nano-SIM card — you can remove it by sticking one end of a paper clip into the hole next to the SIM card slot.
Your device comes equipped with a set of EarPods; these are earbuds with a microphone and remote built onto the right-side cable that can control volume, change tracks, and answer and end calls. You can use these controls to perform a variety of actions with the right combination of taps.
SINGLE-CLICK Clicking the center button of the remote once while listening to music or watching a video pauses playback; if you're receiving a call, a single-click answers it, and another single-click hangs up when you're finished.
SINGLE-CLICK AND HOLD When you're receiving an incoming call, a single-click and hold declines the call and sends it directly to voicemail; while you're on a call, you can do this to switch to a secondary call. Otherwise, holding down on the remote activates Siri.
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