My phone number hacked by someone and they knows all my text .. p

I think someone hacked into my phone or phone of my friend. I am on verizon. I think the hacker have managed to hack into my friend's phone and they have the ability to see all of the text messages he sends me, along with the pictures he sends and knows exactly when he calls. I've told Verizon about my problem and they said the only thing I can do is to change my number. I really don't want to do that.

I don't really understand how they hacked it, I think your friend's mobile is available to that phone call maker. Its not hacked, problem is with your friend or may be your friend is playing prank with you.

But, seriously I am not sure about it. May be I am wrong completely.