answer:
https://forum.xda-developers.com/galaxy-note-8/how-to/decrypt-decode-note-8-omc-csc-files-t3770940
go to
/system/omc/XXX/ (XXX- your country code, my is XEO)
copy
cscfeature.xml to your PC and then use tool from the link to decrypt this file
edit decrypted file in the notepad adding
<CscFeature_VoiceCall_ConfigRecording>RecordingAllowed</CscFeature_VoiceCall_ConfigRecording> ( should be: RecordingAllowed - forum error? ) anywhere, but between
<FeatureSet> and
</FeatureSet> lines
encrypt file using tool
copy file to its original location with proper permissions,
644
Hope this works on Note9 too.