Please ASK before you demand to use a phone number for 2 step authorization.
I choose not to have my phone and email connected in any way.
I have had this email account for 18 years and have never had any problems until Yahoo decided to force me to use a 2 step authorization. I see this as a serious invasion of my privacy. When I first opened the account I gave a phone number. That is all that should be needed. I have accessed my account almost daily since I opened it and I feel that this two step authorization is a serious invasion of my personal privacy and needs to be corrected.