Please I'm appealing to the mobile phone gurus on this platform to help solve my phone's problem. Anytime I dial a number to make call, the phone will just switch off and restart again. it's been a constant problem for some time now. What do you think is the problem and what are the possible solutions you can suggest? The phone is itel 1556 plus. thanks.

FRP is the feature that makes an Android device with a Gmail account not to boot up after factory reset unless the main Google account that was on it is properly entered/verified.

This is why it’s called Factory Reset Protection. It’s also available on Samsung and Gionee Android phones and can be equally removed.
If the 2 methods above couldn’t get your new Itel phone unlocked, try this trick to access Itel recovery menu:

Power off your Itel phone and re-insert the battery. (If it’s user removable).
Press the power button and almost immediately/before the Itel logo comes up (about 3 seconds after pressing the power key), press and hold the volume down button until you get into recovery mode. You should make sure the phone doesn’t vibrate before pressing and holding the volume down button. If it doesn’t work, repeat the process accurately.

If you see a no command with an Android logo, you are almost done! Press and hold the power button for about 2 seconds before pressing the volume up button. The full recovery menu should now come up.

Then scroll down, select Factory Data Reset, confirm it with Yes and after the reset, you can reboot.