Helpful, I’m rolling my eyes but I will answer you seriously.
A child does NOT have a constitutional right to a cell phone. If a parent does give a child a cell phone, it should be with rules. In my opinion, rules include finding out who the child is calling and where they are going. Make sure the rules are known up front.
I also don’t think you have to scrutinize every second of their phone bill, but you should be aware of who they are calling. You need to verify that your chinuch has stuck.
Lets liken it to a car. You teach your teenager how to use one. You get them lessons. They get their license and early on you always drive with them. Then as time goes on, you make sure they get in and check their mirrors and fasten their seat belt before leaving. After a while, all you ask is “Where did you go?” But its still YOUR car and you control it.
I don’t advocate big brother. But I do advocate that parents stay involved with their children and make sure that the freedoms they are giving their children are age appropriate and that their children are responsible. Train, assist and then let them succeed.
At no point to advocate abandoning your children for “trust.”