Voicemail works internally; Not externally?

I have a customer who’s having problems with their voicemail setup. They have each recorded their own ‘greeting’ for people who get their voicemail and when they call locally to test it, it works. However, when they call their DID number, it does not (for DID setup we are using bandwidth.com and have manually keyed in the extensions; I am just using, for example, Voicemail(2000) to send a caller to their voicemail). I have never heard of or read of this issue. If anyone can give me insight on what the problem might be, please let me know.

-This is running on 1.4 svn build on centos (x64)

Alright, we figured out the problem. For some strange reason, Voicemail(user) would not work properly. We had to use Goto(default|user|1) on all our DIDs to make it work properly. Using Voicemail(user) would give us the default system settings instead of the user-recorded greetings. Thanks to all who took the time to look into it.