T46s Firmware Downgrade

Hi!

I installed the firmware 66.9.0.25 on on of my T46s.
But that was a mistake.
This is a Skype for Business Firmware.

As we are using Starface, i need a Starface compatible firmware like 66.81.150.4
A firmware "Upgrade" to an older 66.81.0 is not possible via Webinterface.


Please help!!

Many thanks,
Bernhard