Any cellular whizzes out there ?

Hello people,

My CDMA phone went "missing" and was "found" after a couple of days. Ever since this guy in whose presence the phone went missing has known about all my conversations.

My guess is :

1. It is a cell to cell wiretap.
2. Each time I turn my phone on a message is displayed on his cell phone.
3. He can make normal calls from his cell phone while being able to listen to my calls.

Could someone tell me how many ways can he do this in? So I can check what he did.

Thanks guys!