Change of ownership question!

I am wanting to remove my line off of my dads and change the ownership to my boyfriends account. I know that my dad has to call customer service to remove ownership, but does he also have to consent to my boyfriend taking ownership? Or is he just supposed to take the line off and my boyfriend can take ownership of it without the consent of my dad? When my dad takes my line off, is my phone number and line just in the air for someone (like my bf) to take freely? Super confused!