Is there a way to stop devices getting access to a iphone?

[Phil2008]

Someone has said you can block devices accessing stuff on your phone, but how to you do that?

Basically someone has access to everything on my sisters phone from their phone and she whats somehow to stop this without starting all over again with a new account, phone number etc?

 

[ChrisD.]

How would they have access? Unless the device is under parental control, MDM, or there’s an app the user explicitly allows for remote access it’s not possible.

 

[NetMan]

How would they have access? Unless the device is under parental control, MDM, or there’s an app the user explicitly allows for remote access it’s not possible.

Could also be:

Two devices signed in using the same Apple id?

Family Sharing enabled?

without starting all over again with a new account, phone number etc?

Phone number is only used for account verification, even if she factory reset the phone and created a new Apple id she wouldn't lose the phone number. She can even ask for the PAC code and take the number with her if she wants to use a different mobile provider.


Thread has safeguarding overtones could be a minor trying to subvert parental control or someone trying to leave a coercive relationship...

Is she 18+, can she visit an Apple store?

 

[Phil2008]

This person had access to her phone and screenshot allsort off her phone, so now somehow the person has access to all stuff on her phone?

 

[VaderDSL]

Personal safety overview

This guide is designed to help you manage the personal safety aspects of Apple hardware, software, services and apps.

support.apple.com

Read through this in detail and action accordingly.

 

[NetMan]

This person had access to her phone and screenshot allsort off her phone, so now somehow the person has access to all stuff on her phone?

I can't see how screen shots would be enough on their own, even with her Apple id it would still send authentication requests to her phone. Phone cloning is a thing but rather unlikely...

Unless she is a minor and its a guardian that has done this it would fall under stalking and should be reported to the police.

If they had access to her unlocked phone they could have installed monitoring software, enabled family sharing etc; she needs to sign out of any other devices,disable any sharing, change her passwords etc as per the safety check links in the Apple guide @VaderDSL posted and check what is installed I'd probably factory reset.