to limit hangups you can use "hangupself" instead of hangup so users can only hangup their own calls

If you want fine grained hangup controls, you can use custom permissions, since FOP 2.22 and up. Using fop2admin for freepbx is the easiest way to create them:

1. create a group including the buttons you want the action to be allowed
2. create a permission that includes "hangup" and check the group
3. assign the newly created permission to some user

Best regards,