Trump administration to send U.S. cellphones a test alert on Thursday (reuters.com)

This is a reminder that radio waves are not yours, this is not about your hardware. Your phone number is accessible to anyone, even if you don't give your number out, it's still accessible to someone through random chance (a wrong number, for example.) - there are things we can own that have identifiers, a car is another one of those things, and if the DMV sends you a letter to renew your license, it's not a reminder that your car doesn't belong to you, it's a reminder that the DMV has your details.