Hi there and welcome
Can you tell me the make and model of your phone
And how you were told someone has hacked your phone?
ok.... but the only way to hack your iPhone to a very limited degree is if they have your Apple Password.
This is the only way, and then they can only see limited data such as contacts, photos ect.
But to stop this, please reset your password ***** my link below
Sign into your account here
Below Security, click Change Password.
Follow the onscreen steps.
After you update your password, you need to update your Apple ID in each service that you’re signed in to.
To do that, Go to Settings > iTunes & App Store.
Sign out then in with the new password
This stops any further access to the phone
If you have any problems, or would like any additional information or assistance, please do not hesitate to let me know.
Else if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.