Well, it should be located on Cisco SPA112 2-Port Phone Adapter product page. But Cisco pages are broken a lot - complete PDF book is not available. So I attached a copy of such file I downloaded from Cisco pages in the past here. It may not be latest version of document ...
Did you consider simple answer ? Just because the PBX told the adapter that there is message waiting, so adapter told it to phone ? Turn on syslog&debug, catch them as well as SIP dialog to confirm or reject such conclusion.
cann't tranfer calls
Not possible to respond. You didn't disclosed your configuration related to call transfer. Your call transfer request may not be recognized by SPA adapter or it may be rejected by PBX. Turn on syslog&debug, catch them as well as SIP dialog to identify the source of problem.
You have a Cisco Unified Communications Manager (CUCM) system and want
to configure a SPA112 analog telephone adaptor (ATA) to register to the
CUCM so that you can use up to two analog phones or similar FXS devices
with the CUCM.In this application note, ...
This document is a must-read for all SPA232D installers, administrators,
and users. The document takes you from unboxing the SPA232D ATA and
SPA302D DECT handsets, through DECT handset registration, and connecting
to the PSTN and ITSP.The document describ...