Now I changed my iphone5, so I gave my mother my old iphone4. Why do I use my current mobile phone to send text messages and my previous mobile phone can also receive them?

Icloud is synchronized, just change your mobile phone ID.

Settings-general -icloud, logout.

Reach out to others, or restore the system is better, otherwise embarrassing problems will always appear inadvertently.

Setup-Restore-"Erase all contents and settings" (without upgrading the system).

Use itunes to restore the system.

1. Install iTunes. Start iTunes.

2. Insert the iPhone, press and hold the power button and the Home button 10 second, wait for the iPhone to go black (according to experience, it is about 0.5- 1 second after the black screen), release the power button and hold it down.

Until iTunes approved the iPhone.

3. At this time, Windows will first find some new hardware and drive it by itself. After iTunes automatically recognizes the iPhone, a prompt box will pop up. "iTunes has detected that the iPhone is in recovery mode. You must restore this iPhone and use it with iTunes. " Click OK at this point.

4. Open itunes, and click "Restore" in the section showing iphone capacity and information to start the recovery process.

5. Before displaying the picture of the data cable connection on the iPhone, iTunes will prompt that the firmware recovery is completed.