can't erase phone

If the screen no longer works you would probably need to put it into recovery mode to erase it.

See the steps here:

If your iPhone won't turn on or is frozen - Apple Support

You can follow the steps under:

If your iPhone turns on but gets stuck during start up

Good luck!

Hi, if you are going to reset your iPhone to factory settings follow these steps:

Erase iPhone

When you delete data, it’s no longer accessible through the iPhone interface, but it isn’t erased from iPhone storage. To remove all of your content and settings from storage, erase iPhone. For example, erase iPhone before you sell it or give it away. If you want to save your content and settings, back up iPhone before erasing it.

You can erase iPhone from Settings . If you’re unable to open Settings, you can use a computer to erase iPhone.

Wipe all content and settings from iPhone

1. Go to Settings  > General > Transfer or Reset iPhone.
2. If you’re erasing your iPhone because you’re replacing it with a new iPhone that you have on hand, you can use extra free storage in iCloud to move your apps and data to the new device. Tap Get Started, follow the onscreen instructions, then return to Settings > General > Transfer or Reset iPhone.
3. Tap Erase All Content and Settings.

When iPhone restarts with all content and settings erased, you have the option to set up iPhone as new or restore it from a backup. See Turn on and set up iPhone.

Note: If you’re asked to enter your passcode and you’ve forgotten it, see Reset the passcode. If you’re asked to enter your Apple ID password and you’ve forgotten it, see the Recover your Apple ID website.

Use a computer to wipe all content and settings from iPhone

You can use a Mac or Windows PC to erase all data and settings from your iPhone, restore iPhone to factory settings, and install the latest version of iOS. For example, if you can’t open Settings  on iPhone, you can use this approach to restore iPhone to factory settings.

Before iPhone is erased, you have the option to back it up. If you make a backup, you can use the backup to restore your data and settings on your iPhone or on a new device. See Restore iPhone from a computer backup.

1. Connect iPhone and your computer with a cable.
2. Do one of the following:

• On a Mac: In the Finder sidebar, select your iPhone, click General at the top of the window, then click Restore iPhone.
  • To use the Finder to restore iPhone to factory settings, macOS 10.15 or later is required. With earlier versions of macOS, use iTunes to restore iPhone.
  • On a Windows PC: Install or update to the latest version of iTunes on your PC (see the Apple Support article Update to the latest version of iTunes). Open iTunes, click the iPhone button near the top left of the iTunes window, click Summary, then click Restore iPhone.

2.Follow the onscreen instructions.

Obtained from: Erase iPhone – Apple Support (UK)

Hope this answer will help you