I'm in a wired situation, I opened my facebook account with a phone number, not email, my username is phone number I had ~5 years ago. I lost the sim card ~4.5 years ago, so since then I still use the same login. Every time I login facebook asks me to update my phone number because it's no longer valid, so they probably know it's been recycled and someone else owns the number. Another thing... a year ago, I got a new sim card with new phone number again (I change my number every 1-2 years), and since that time I can't use this phone number to setup 2FA because... someone else on Facebook has this number in their profile!