When I called a voicemail number, I noticed the following errors in the Asterisk console:
[Apr 10 17:08:01] WARNING[19135][C-00001cf4]: file.c:701 ast_openstream_full: File digits/1n does not exist in any format
[Apr 10 17:08:01] WARNING[19135][C-00001cf4]: file.c:1017 ast_streamfile: Unable to open digits/1n (format (ulaw)): No such file or directory
[Apr 10 17:08:01] WARNING[19135][C-00001cf4]: file.c:701 ast_openstream_full: File vm-newn does not exist in any format
[Apr 10 17:08:01] WARNING[19135][C-00001cf4]: file.c:1017 ast_streamfile: Unable to open vm-newn (format (ulaw)): No such file or directory
Errors are caused by the lack of sound files, for example, in my case in the voice mail one message and when I try to say “you have one (1n.ulaw) new (vm-newn) message, an error occurs and the handset lies down.
Archive with a set of necessary files is enough to simply download from the official site and unpack to the directory /usr/share/asterisk/sounds
After this, the error should not be.