You can reach a point where the phone number you used for 2FA has been "used too many times" and then you're stuck in the middle of registration. There doesn't seem to be any documented limit anywhere and the only solution people have been able to use is find someone else to help you verify with their phone number. What makes this more difficult is when you get logged out of one of your accounts, they ask for a phone number for 2FA to login, you provide the same phone number you used originally (even though it is not officially associated with your account, just to verify registration), but that fails because your number has apparently been used too often. So now you can't even log in to your valid account that already exists. Sure, should have added some other form of 2FA or a passkey to the account, but why can't I verify with the same number I used originally? And just to top things off, you can't use your Google Voice number for 2FA account verification when signing up for another Google service.