Clear Skype for Business or Lync Temporary Cache Files

Follow instructions here: https://www.cosocommunity.com/hc/en-us/articles/200887737-How-to-Clear-Lync-Temporary-Cache-Files

In path for the location where temp files are stored, use \%AppData%\..\Local\Microsoft\Office\16.0\Lync\ for SfB.
use \%AppData%\..\Local\Microsoft\Office\15.0\Lync\ for Lync.

I Can't Disable Lync or Skype-for-Business Forwarding

Occasionally a call forwarding rule configured in the Lync/Skype-for-Business environment won't delete or remove properly. More often than not, updating the user database will flush out these unwanted configurations.

See Microsoft documentation here: https://technet.microsoft.com/EN-US/library/gg398682.aspx

References:
https://technet.microsoft.com/EN-US/library/gg398682.aspx