iPhone: If you can't send or receive text messages

If you can't send or receive text messages

• Check the top left corner of iPhone's display to make sure you have a strong signal: If you don't have a strong signal, try moving to a different location. If you're indoors, try going outdoors or moving close to a window.
• Update to the latest iPhone Software. For more info, see Backing Up, updating, and restoring your iPhone and iPod touch software.

If you still can't send or receive text messages:

• Ensure that you are first tapping in the text-entry field at the bottom of the screen (highlighted in red below) to bring up the keyboard. Until you begin typing, the Send button will remain grayed out.

• Power off iPhone, then turn iPhone back on.  Press and hold the Sleep/Wake button until the red slider appears. Slide your finger across the slider to turn off iPhone. To turn iPhone back on, press and hold the Sleep/Wake until the Apple logo appears.
• Make sure that every phone number in your contacts list includes an area code.
• Make sure Airplane Mode isn't on. From the Home screen choose Settings, then turn Airplane Mode off.
• If you are trying to send a text message to multiple recipients and you type in each number manually instead of using the contacts list, make sure you tap return instead of space to separate each one. For more info, see Sending SMS messages require a valid 10-digit mobile number.

Note: Both SMS and MMS support text messaging. If Show Subject Field is enabled in Settings > Messages > MMS > Show Subject Field, you can only send messages after you have typed content in the Body field. Until then, the Send button will be grayed out, and you will be unable to send the message. If you add text to the Subject and Body field you will automatically send via MMS. If you wish to send via SMS, not MMS, either type text in the Body field only, or disable the Show Subject Field option. The following table illustrates this relationship: