When i dial a number the phone cuts off and restarts

Please try resetting the phone to default settings and it should work. The default code should be the last 4 digits of your phone number unless you have changed it.

Restoring Phone Memory to Factory Conditions

This returns all settings to their factory default value and erases all user data including pictures, video, music, messages, contacts and downloaded applications stored on the phone.

1. From the home screen tap MENU.
2. Tap Settings & Tools.
3. Scroll th screen up and tap 7.Phone Settings.
4. Tap 5.Security, You're prompted to enter the lock code.The default lock code is the last four digits of your telephone number.
5. Enter the Lock Code and tap DONE. The security menu appears in the display.
6. Tap 5.Restore Phone. A prompt appears in the display asking if you wish to restore default settings and erase all user data including pictures, videos, music,messages, contacts, and downloaded applications stored on the phone.
7. Tap Yes to reset and restore default settings or tap No to return to the Security list.