how do you restart your phone if it blacks out

Hello there, Klayaa.

It sounds like your iPhone's screen is black even though you are hearing notifications from calls and text messages. The following Knowledge Base article offers up some thorough troubleshooting steps for that very issue:

If your iPhone, iPad, or iPod touch doesn‘t respond or won‘t turn on

If your screen is black or frozen

First, try to force your device to restart.

• Forcing your device to restart won't erase the content currently on your device.
• You can force your device to restart even if your screen is black or your buttons aren't responding.

Press and hold the Sleep/Wake and Home buttons at the same time for at least 10 seconds until you see the Apple logo.

If your device still won't turn on or start up

Plug in your device and let it charge for up to 1 hour.

After a few minutes, you should see the charging screen.

If you don't see the charging screen within an hour, or you see the connect to power screen, check your connector, USB cable, and power adapter. Make sure that everything is plugged in firmly, free of debris, and not damaged. You might want to try a different USB cable or power adapter.

If your device still won't turn on, see what to do next.

Thanks for reaching out to Apple Support Communities.

Cheers.