I sure I have an account with somebody through AT&T. We have two iPhone fifteens and iPhone 16. I’m trying to find out if the girl that owns the account and is in her name is able to spy on my phone.
She can view the numbers for the calls you make and receive from the cell provider, since she is the account holder. Messages are not viewable, but the contact information is. That information comes from AT&T, not from your device.
She has no access to your device just be sharing the same cell provider. The only way that would be possible is if you were using the same Apple Account.
I think you need to make clear what you mean by"account". There's the account that is held with ATT and then there's Apple Accounts. The two are not associated (see Mac Jim ID's reply) but if you are also sharing a single Apple Account or ATT's NumberSync then your information is at risk.
Things we need to know:
1) Are you using ATT's NumberSync service?
2) Do each of you have your own Apple Account?
I know you say you have a shared plan, but some cell providers offer multiple number plans so each person has their own number but there is a single main subscriber. The last time I asked ATT, they did not offer that, but that was a couple of years ago. We need to know exactly what kind of plan is involved, but omit any personal information.
To be clear … you DO each have your own, unique Apple Accounts … right ?
If you are concerned why don't you have your own private account? Why are you using a shared plan?
how can I tell if my iPhone 15 on a shared account is being spied on by the account holder
