Mobile Friend List

Under my son's device for messaging, it displays the contacts from my phone and not his.  This results in my not being able to block or unblock any of his contacts.  The message " Your activity is being monitored..." gets repeatedly sent over and over again (he is allowed to send text messages to friends who it says are blocked). I tried to uninstall the application, but it won't let me do that either. Please let me know how I can fix this.  Thank you.