Secondary extension possible?

We cutover to a FreePBX today from trixbox. As part of the migration we changed our extensions from three digits to four. I created a SIP alias with the old three digit extension and it works internally fine.

The problem is when I call into the IVR and dial the old extension it does not work. The new extension works fine.

So my question is, without creating another extension for every user with their old extension is there a way to add the old extension to their new one?