hacked iphone iPhone 4S

Those are all strange occurences for sure.  Is you iPhone jailbroken?  Have you loaned it to anyone for a few hours?  If so, it could be.  Non-jailbroken iPhones can't really be 'hacked'

That being said, try restoring with you backup.  If you still have problems, restore as new, i.e. without your backup.

phone has not been jailbroken. I was talking to a co-worker about this and he was telling me about an app that is out that can prank phone call and text people phones. He thinks this may be a friend of pranking me as far as the text message is concerned. I just need confirmation that iphones can not be hacked. If they can't be then, then I'm just going to say the other issues are carrier related and that maybe one of my friends is pranking me with that app as far as the text messages are concerned.

He thinks this may be a friend of pranking me as far as the text message is concerned.

That is almost certainly the case.

I just need confirmation that iphones can not be hacked

Unless your iPhone has been jailbroken, the chances that it has been hacked are vanishingly small. If you still suspect a hack, though, restore the iPhone to factory settings. That would remove any even theoretical hack.

Regards.