Does not listen to messages, the first message I get a busy signal.

Immediately after the entry that indicates that the message was received at 00:00 on the day you play a busy signal.

On the cisco phone (spa 504G) the call is ended before the busy tone

Thank you for any informations, Gil
p.s.Report what follows from the following link perhaps explaining why the line is dropped listening to messages
http://www.voip.ammdomus.it/index.php?option=com_content&view=category&layout=blog&id=3&Itemid=4"Mancavano invece alcuni suoni sotto "digits" ("e" "hours" "minutes"). Essendo usati in quella posizione solo dalla lingua italiana, la loro mancanza provoca la CADUTA DELLA LINEA anche in compresenza del set inglese (non venendo trovato un equivalente sotto digits nemmeno in quella lingua)..."