Bluetooth device still paired after clean install
Just to clarify, have you tried either of the following:


On the MacBook Pro go to System Preferences > Bluetooth and right-click on the device (his iPhone) and select Remove
On his iPhone, go to Settings > Bluetooth and tap on the 'info' icon on the right of your MacBook Pro  and then tap the Forget This Device option


Doing this should solve your issue. For good measure, I would do both.

If the above steps don't work, try resetting the iPhone settings. Your co-worker can do this on his iPhone by going to Settings > General > Reset > Reset All Settings. However, make sure he has his passcode and Wi-Fi passwords handy.

Finally, if you happen to not be using any Bluetooth devices with the MacBook, you can also turn it off totally from System Preferences > Bluetooth.