They already have your mobile phone number because banks and credit lines you take will report that information to them. They ask you for your phone number to

They already have your mobile phone number because banks and credit lines you take will report that information to them. They ask you for your phone number to verify you, not because they want your phone number when they already have it. If you want to avoid them knowing your "real" phone number and leaking that to marketing agencies, the best thing you can do is get 2 mobile phone numbers, one you actually use with your friends and family, and one you provide to businesses and stick that SIM in a beater phone and keep it silent. I HATE this system and wish we had some GDPR-like law for preventing sharing of such information outside the corporation you provide it to, but such is the current state of the system in the US.