Asterisk DID Question

I have a pretty limited knowledge of Asterisk. I’m trying to write an extension to my extensions.conf that will allow Freedigit calls to go to extension 3001. They ring the extension but will not go to voicemail on my system. I’m getting the error of [Jun 6 09:47:00] NOTICE[4018]: chan_sip.c:15092 handle_request_subscribe: Received SIP subscribe for peer without mailbox: 3001
on my console.

Here is my extension configuration for the DID in extensions.conf:

[did_freedigits]

exten => s,1,Dial(SIP/3001,20)
exten => s,2,Voicemail(3001,u)

Any ideas what is wrong? I’ve Googled the heck out of this and am hitting a wall.

I do have voice mail setup for extensions in voicemail.conf…

[default]
3000 => XXX,Joe,joe@gmail.com
3001 => XXX,John, john007@gmail.com

Fixed it. 20000 ms was too long for the voice mail to pickup before it went to the default Free Digit voice mail.