There are a couple of different approaches to accomplish this depending on call volumes and other requirements that you may have - I won't ask about all your requirements and let you try to match up the best approach:

- remove the phone number from the extension, forward all incoming calls to the extension to the phone number of the physical phone (this only works if you are using cell phones or other non-rc-voip phonesets - for example, our company only uses cell phones so we forward all calls to our staff)

- add a custom rule that transfers all calls coming in to that users phone number back to the IVR menu. The IVR transfers calls to the users via their extension not the number, so the IVR transfers will still be allowed through. This option is not obvious on how to set it up, the trick is to not answer any calls, then in the message options, you set the calls to go to group, then then IVR extension will be available to select.

- add a custom rule, like above, but send it to a custom msg the instructs the caller to only use the main number. Depends on if you want to train callers to use the proper number, or don't care what number they call and just want to ensure they are filtered through the IVR

There are a few other approaches I have read about, but the above ones are the only ones we have actually tried and are using.

Hope this helps

Per your suggestion I was able to add a custom rule that dumps direct calls to that number with an announcement ("Please call the main number instead..."). Brilliant. Thank you so much for taking the time to help!!!