The settings icon is a series of gears one inside of the other in a silver or gray box. It is labeled settings and can be seen on the 'Home screen' of the iPhone that is being pointed at in this example. Tap it once to open the 'Settings' panel.
This should include the country and region, or area code as well. For example, if you were in Washington, DC in the United States you would enter in +1 and then the area code for Washington, DC, which is 202. Alternatively, if you live overseas as I do, you are going to enter a different code. In this example, we use that code.
Press and hold the 'Power button' or 'Lock button' located on the right side of the phone, and swipe on-screen button to power off the phone
The reason I'm restarting the phone is to make sure the system has enough time to reset itself. Sometimes we can be a bit impatient with technological devices. Therefore, it is important that we wait a few minutes to make sure everything updates properly.
Press and hold 'Lock button' again, until you see a white apple appear on the screen, at which point your phone is restarting
The other reason I am restarting the phone is that sometimes phone settings, even when they are deleted, do not actually delete or may take a little time to update. Any time a technology related product is not functioning the way you want it to, restarting it should always be one of your first troubleshooting options.
As we can see, our correct phone number has now been listed here at the top. This corrected phone number will allow me to use iMessage through the messaging service. It may take a moment for it to activated, as sometimes the server system is not as quick as we would like it to be. However, as you saw, my phone number has now been correctly updated activated and synchronized with the iMessage servers on the Apple side. Tap the arrow in the top left to return to the 'Settings' panel.
After we choose a number or contact to send a message to, we can see that the blue highlight indicates that it is an iMessage that will be sent
If we type in another contact we will see it become highlighted green, which indicates it can not send as an iMessage and only as a standard SMS. Removing the second contact changes the setting back to iMessage.