My ex-husband paid for my 3 teenagers phones for 3 years. He wouldn't upgrade them and he bought the cheapest, crappiest phones he could find. My daughter's quit working about 2 months ago. My son's quit a week ago. He just bought an old (but not horrible) flip phone for him. And even though hers broke long ago, he has no intention of replacing my daughter's phone. She said it was because he "doesn't give a crap" about her "and he never did". Sadly, she's pretty accurate on that one. My oldest son used to be the only important child to him.
So get this, a few months ago he told me he could no longer afford to pay for HIS 3 teens' phones anymore because he pays for his step-childrens' smartphones. He doesn't see anything wrong with this because he's not the one that got them their smartphones.
This leads us to the secret. I added 3 new lines to my account and got them new smartphones with new phone numbers. My teens decided (without my input) that they didn't want their father to know their phone numbers so he doesn't even know they have new phones. He never sees them and really has nothing to do with them. His current wife won't let him because she wants him to "father" her children from various different men.
A dear friend of mine (who is as a VERY GOOD counselor) thinks we should tell him so we are not keeping a secret. I told her they didn't want him to be able to call them. She said we could just block his phone number. I think that would do more damage than than good.