Hello @froggy1n
I don't believe anyone can hack a iPhone unless they have your Apple ID password and any passwords associated to your accounts / apps..
First would be to change all passwords and do a clean factory reset on the device.
If you feel like you want to go an extra step, the if the device is under warranty I would make a appointment with their closest Apple store to you and have them exchange it to another same iPhone as urs. Make sure once again to change all passwords to all accounts u have.