@Nikita
try this (credits to srlawren)
dial into your voicemail and log in with your PIN.
In the main menu, press 3 (manage greetings),
then 4 (manage extended absence greeting),
then 2 (record a new extended absence greeeting) and record a message that indicates to your caller you are not accepting messages.
Then press 4 to turn on extended absence
Finally, press 5 to dissallow anyone to leave you a message.
