Using the myATT app on your smartphone you can turn off mobile data on any device on your mobile share group. I do not believe that you can use the app to disable voice service, or wifi access though.
If the phone in question is an iPhone, you oculd use Find My iPhone from Apple to remote lock the phone where the phone holder would need to enter a passcode that you specified when you locked it in order to be able to use the phone again. This could be used in a pinch, but be aware that if you lock a phone this way, it might be possible for the person to attempt too many incorrect codes, and cause their phone to be reset back to factory defaults losing information from their device (pictures, messages, etc.).
If the phone in question is an iPhone, you oculd use Find My iPhone from Apple to remote lock the phone where the phone holder would need to enter a passcode that you specified when you locked it in order to be able to use the phone again. This could be used in a pinch, but be aware that if you lock a phone this way, it might be possible for the person to attempt too many incorrect codes, and cause their phone to be reset back to factory defaults losing information from their device (pictures, messages, etc.).