Is my wife cheating on me?

My wife went out last friday with her girlfriends to a club later on that nite her phone call me i listen to see who she was talking to it was a guy in her car i listen about 20mins the phone cut off i call her back she did answer her phone so later that night she called an i said where are u she said at the club so i ask her who was in the car with u she said nobody i said stop lieing i heard u two talking your phone call me than she said we was at a club an wanted to go to another one an he ask can he go she said yeah so he road with her now i ask her did u know him she said from highschool he was already they i didnt know i made a bad mistake so is my wife cheating on me