How do I delete all my contacts from my iPhone? All at once!!!

Settings, (your name), iCloud, turn off contacts.

Settings, Contacts, accounts

Tap each account and turn off Contacts

Any remaining ones are “on my phone” contacts and you can delete the Contacts app to clear those. Reinstall from App Store.

If you use iCloud contacts:

https://support.apple.com/en-gb/guide/icloud/mme6182cfc37/icloud

If you don’t use iCloud then you cannot recover it.

Recovery of a deleted number