Apple iMessage is a pleasant alternative to regular SMS messages. Send comfy messages from iPad or Mac that does not support SMS text messages. If you send iMessage to a person with multiple devices, the message will appear on all devices. However, since iMessage can use cell data if it is not connected to the Wi-Fi network, some people may choose not to use it on the iPhone.
iMessage is sent using Wi-Fi or mobile data. When Wi-Fi is available, iMessage is sent over Wi-Fi. If a Wi-Fi network is not available, iMessage will be sent with cellular data. If you regularly approach the monthly limit for your data plate, you can try switching off iMessage to save your mobile data usage.
When you open the Settings app on your iPhone, select Messages and set the iMessage slider to off position, you will not send or receive iPhone iMessage. However, depending on your location, you may not receive text messages from iPhone users. Also, if you have more than one Apple device, iMessages can still be transferred to other devices. This is usually not desirable. Most people want their messages to go to their iPhone.
To understand what's going on, let's look at iMessage more closely. When you first set up an Apple device, the Apple ID automatically logs into the Messages app. When your device is iPhone, your phone number will be associated with your Apple ID for use with iMessage.
If a person with an iPhone sends a message to your phone number, the Messages app will communicate with Apple's servers and find your phone number. The Sender messages application sends the message as iMessage. If a person with an iPhone sends an iPhone message to iPhone, the Messages application will not find the phone number on Apple's servers and send the message as an SMS message.
Turning off iMessage
Turning off iPhone iMessage slider stops iMessages for delivery to iPhone. However, it does not prevent iMessage from being sent to Apple ID. Consider the situation when someone has an iPhone and an iPad. Stopping the iMessage slider on a device will still allow iMessage to be received on another device.
Even when the iMessage slider is off, the phone number is still associated with your Apple ID. Therefore, if other iPhone users send you a message, you will send them as iMessage. But since the slider is off, the message is not coming to your iPhone.
Receiving All Messages as Text Messages
If you want to turn off iMessage and send all messages as an SMS message to your iPhone, you need to interrupt your phone number and Apple ID beginning on. Simple disabling of iMessage does not interrupt the association.
To remove the phone number from your Apple ID, first make sure iMessage is turned off on your iPhone. To do this, open the Settings application, select Messages, and set the iMessage slider to the off position (not visible in the slider).
Then go to Apple's website and modify your Apple ID password. By changing your password, you can effectively enable iPhone to use Apple's services until you can re-authenticate it with the correct password. With iMessage enabled by the iPhone, Apple's servers will no longer associate their phone number with your Apple ID.
After you have changed your password, you need to sign in to services such as iTunes & App Store and iCloud.
Do not sign in to Settings -> Messages and do not turn on the iPhone iMessage slider. To do so, you will re-associate the phone number with your Apple ID.
Now that a person with an iPhone sends a message to your phone number, the Messaging application will not find your number on Apple servers and the message will be displayed as an SMS message through your mobile service provider. Regular text rates apply.