iPhone possible hacking

My young daughter tried to contact her friend via iMessage. Her friend's account is set up via her father's email address. My daughter later received unsavoury texts back. She deleted these straight away as there were swear words and she felt guilty about them.

One message remained on the iPod. It came from the father's email address, he claims that there must be a crossed line or his iPhone has been hacked.

Is either of this possible?

Iphone, was not hacked. wasn't crossed. Husband was arrested and admitted to charges.

Thanks for help, it confirmed that the device was probably not compromised.