Permissions on voicemail directory

Hello I’m developing a web service for managing voicemail.
I need to read archieved files to send back through web service but since web services are executed as Apache’s user I can’t read files in /var/spool/asterisk/voicemail/context/number/Old nor files in Family, Friends and Work directory, but I can read only files in INBOX folder.
www-data belongs to asterisk’s group but I haven’t read permission for the group on the archieved files.

What is the reason of this choice of changing permissions?
And is there a way to read the files maybe through Asterisk?

I think there could be an option for setting permissions on archieved files.

Any help would be appreciate