Noted, and prayer beginning!
My neighbor in Oklahoma took the door off her son’s room. Sold his stereo, too! Bill and Tom share, so we’re not quite ready to remove the door, but changing the knob is a strong possibility.
Do you have wireless internet? Can you manage the access point yourself? One of the things you can do is set your access point so that only specific MAC addresses can connect. (A MAC address is an actual physical address tied to a specific device.) You can tell him that whenever the door is closed his, and only his, MAC address will be disabled. You'll re-enable it when his door is open.
I bet that would get you some attention, unless he has a 4G unlimited data plan on his phone.