How to Troubleshoot iPhone Problems with Calling or Networks
If you’re having problems making or receiving calls on your iPhone, problems sending or receiving SMS text messages, or problems with Wi-Fi or your wireless carrier’s data network, the techniques here are short and sweet — except for the last one, restore. The inconvenient, time-consuming restore technique entails erasing all your data and media and then restoring it.
First, here are some simple steps that may help. Try them in this order:
Check the cell signal icon in the upper-left corner of the screen.
If you don’t have at least one or two bars, you may not be able to use the phone or messaging function.
Make sure you haven’t left your iPhone in airplane mode.
In airplane mode, all network-dependent features are disabled, so you can’t make or receive phone calls, send or receive messages, or use any apps that require a Wi-Fi or data network connection (that is, Mail, Safari, Stocks, Maps, and Weather).
Try moving around.
Changing your location by as little as a few feet can sometimes mean the difference between four bars and zero bars or being able to use a Wi-Fi or wireless data network or not. If you’re inside, try going outside. If you’re outside, try moving 10 or 20 paces in any direction.
Keep an eye on the cell signal or Wi-Fi icon as you move around, and stop when you see more bars than you saw before.
Try changing your grip on the phone (or if it’s an iPhone 4, try using a case).
Apple says, Gripping any mobile phone will result in some attenuation of its antenna performance, with certain places being worse than others depending on the placement of the antennas. This is a fact of life for every wireless phone. If you ever experience this on your iPhone 4, avoid gripping it in the lower-left corner in a way that covers both sides of the black strip in the metal band, or simply use one of many available cases.
Turn on airplane mode by tapping Settings on the Home screen, and then tapping the airplane mode On/Off switch to turn it on. Wait 15 or 20 seconds, and then turn it off again.
Toggling airplane mode on and off like this resets both the Wi-Fi and wireless data-network connections. If your network connection was the problem, toggling airplane mode on and off may correct it.
Restart your iPhone.
Make sure your SIM card is firmly seated.
A SIM (Subscriber Identity Module) card is a removable smart card used to identify mobile phones. You can change phones by moving the SIM card from one phone to another.
To remove the SIM card, straighten one end of a fine-gauge paper clip and stick the straight end gently into the hole on the SIM tray, as shown here for the iPhone 4 and 4S and for the nano-SIM used in the iPhone 5.
When the SIM tray slides out, carefully lift out the SIM card and then reinsert it, making sure it’s firmly situated in the tray before you gently push the tray back in until it locks.
Performing a restore deletes everything on your iPhone — all your data, media, and settings. You should be able to put things back the way they were with your next sync.