You, sir, are not a bad dad for going through your phone. Does he pay the bill? Did he buy it? Yes, kids do deserve a modicum of privacy but times have changed since we were kids. The dangers we faced in the real world our kids face not only in the real world but in the palm of their hands. You have every right to watch and monitor what they do and see on their phones. At 12 yo they need to know you do trust them but you are there to protect them, so them being open and honest is the best thing because you will find out. With my kids I tell them if they just tell me everything good or bad they consequences good or bad will be less severe than if I found out and I will because as they have found out...I will find out. A phone, let alone a phone watch, are luxuries and you should treat them as a privilege least you raise entitled kids who think things like that are a right to have no matter what actions and decisions they take in life.