How to tell if your phone is hacked
My phone is not working properly sometime. It’s go off by himself and it’s very slow and I have contacts that I don’t have before so many things that I never did.
if a person could hack your phone then their motive to do so would be to try to steal your identity / creditcard info and the likes, they would attempt to do so in a way where you would be none the wiser, because if you were then you would cancel the creditcard and the likes.
so it would not be logical for them to make your phone act strange and make a notice of their doings
if it was me then I would suspect a software issue and try steps like
Force restart iPhone - Apple Support
if you really think someone has access to your account then read
If you think your Apple Account has been compromised - Apple Support