My child has had an old iPad of mine from work since little which is used with her Apple ID as part of our 'family' setup. She has apps games etc linked to it.
Her father (not lived with her since she was 1) has bought her a new iPad recently as she's complained about the old one to him. (Brief backstory: I'm absolutely skint because he pays what he wants which isn't very much unsurprisingly. He is, objectively, loaded)
He has created a new Apple ID for her, linked to him,
(Another backstory 🤣;He has history of cloning our devices and using my emails to access financial details. As you may see there's a lot of history behind all this which is why I need objectivity from you all)
The new Apple ID means her siblings/ cousins/ friends/ me don't have her as a contact. I could message them all to tell them about the new Apple ID but I don't want to. I am 100% sure he will have this device mirrored on one of his Macs. I don't want him privy to all the random little things we send. She's only young (9) so it is only used at home for Minecraft etc.
Lastly, she spoke to him on it in the week and I heard him say 'remember the deal. You answer every call from me or you don't get to keep the iPad.' She said she'd been at her club so hadn't been able to call. He explained she must call straight back when she can, she had 4 missed calls from him so in the future that would mean she has to give the iPad back.
IBU: just change her details with everyone and use the new Apple ID and iPad going forward.
INBU: Get her another iPad with her old Apple ID on so she can privately message whoever she wants, and doesn't have it's use tied to calling an adult.