How do i change the contactable phone number on my apple id account

so recently I connected my boyfriends phone to my apple id acount and icloud but when i got a phone call from my contacts to my phone, the call popped up on my boyfriends phone aswell. So to resolve this he created his own one and singed out of my apple apple and icloud BUT when i try to log on to my icloud on my phone it says it needs a verification code put into a device, so I checked my apple id on the internet and it says my boyfriends phone number as the contactable phone number. So i called him and told him to log back into my account and remove his device from my apple id and it did but the number still hasn't changed. How do i change it back to my number? And are calls to one phone supposed to be linked to the other when coneccted to thw same apple id and icloud