How to resolve a hacked iPhone using someone else's iCloud account?

Sorry to hear your sister hacked her own iPhone by foolishly entering somebody else's account information.

Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Read the requirements and steps for an Activation Lock support request at: https://al-support.apple.com/#/additional-support and links at the bottom right for the type of service requested. Apple says they may require "proof of purchase documentation” and that you need “proof of ownership documentation”, but does not detail what currently constitutes proof other than it “must include the product serial number, IMEI or MEID.” User reports on this community indicate that typically Apple will ONLY accept an original receipt issued by Apple or an Apple Authorized Reseller. Presumably this is the only kind Apple can authenticate against fraud since Apple is not involved in third party sales. Apple recommends that you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support

Note that the device cannot have Lost Mode set on it. If your device has been taken over by you having entered a scammer’s Account then the scammer has likely set that too and the device is lost to you.

If Apple resets the device this will give you access to the device but won't restore access to the account used to lock it. There is nothing that can be done to expedite an Activation Lock request.

abasito wrote:

Hi, my sister's phone was hacked. She's using someone else's iCloud account. How can I solve this?

[Re-Titled by Moderator]

Original Title: Sister's

Should we assume that your sister has signed out of her account, then used someone else’s Apple ID on the phone? If so, the device is not “hacked”, but your sister did turn over ownership to that other ID. If this is the case, please see: How to remove Activation Lock - Apple Support