Siemens Silent Alert Problem

Since my newer cell phone failed, I have reverted to my Siemens S55.
Unfortunately, I have not been able to configure the phone to vibrate
(silent alert, as they call it) but NOT ring on incoming calls. It
vibrates on the Normal profile, but it does not vibrate on the Quiet
profile, even though Silent Alert is ticked in both profiles.

Is there a solution? There are posts on the Internet about updating the
phone's firmware, but the manual does not mention how to do so, and I do
not have a data cable, which is probably required.

I even tried to set the phone to ring and turn down the ringer, but it
will not turn down to quiet.