Isn't that regulated? In many places the operators are required to let you take the number with you when you change provider to obtain a better/ cheaper service. Everybody's numbers in practice go via some LUT that's mapping a human "telephone number" which people dial to an actual service endpoint which might move (after all, cell phones already move, so this indirection was necessary to make that work) and so the rule only needs to say that there's some means by which company A gets to change the LUT for your phone instead of company B.
Isn't that regulated? In many places the operators are required to let you take the number with you when you change provider to obtain a better/ cheaper service. Everybody's numbers in practice go via some LUT that's mapping a human "telephone number" which people dial to an actual service endpoint which might move (after all, cell phones already move, so this indirection was necessary to make that work) and so the rule only needs to say that there's some means by which company A gets to change the LUT for your phone instead of company B.