They are giving out their phone number to people they met on roblox.
The child is institutionalised, their parent cannot control their behavior meaningfully and the adults at the institution are pretty negligent and she doesn’t trust them.
I have messaged like my whole family and some friends for advice but nobody is getting back to me.
In general, I’d explain to a child why this is a bad idea and try to get them to articulate to me why they’re doing it.
There are some possible technolgical solutions I’m sure with phones that can only make or receive calls to specific approved numbers.
Okay so her phone is limited but it can be subverted pretty easily with apps, and the adults are negligent enough that she can flaunt that in front of them.