After firmware update (T46G), No Service, can't login

[Cory]

After attempting to load Firmware version T46-28.81.0.25 from Yealink's web site, 2 of my 5 phones I've tried updating are now unusable.

They rebooted and downloaded for about 20 minutes, but now, they say "No Service" , and I cannot log into them using either the default Yealink credentials or my Vonage credentials. Also, the firmware shows to be 28.81.193.15.

Why would this break my phones?
Why did the credentials change?
Why is the firmware shown on the phone screen higher than the firmware I downloaded?

What can I do to fix this?
I desperately need help.
Thank you.