Did he ask you to put in all this effort, to give him "tips and advice" and to effectively become his personal trainer? Or that a role you assigned yourself?
It sounds like you should just let him do his own thing at the gym. He knows how to use the equipment / weights now, so just let him get on with it.
If he wants to spend half the time on the phone, then let him. He's not harming you by doing so. (Unless you count your bruised ego because he's not diligently following your every instruction.)