From the info you posted, I have one crucial question. You mention that your KSU is a Meridian. What kind. A modular ics, 8X24, or a 616. Call pilot voice mail is only compatible with software versions 4.1 and higher. If you have a 8X24 or 616 then your callpilot is not compatible. If you have a MICS you need to have a software of 4.1 or higher. If you have one of the older softwares, you need either a startalk or nam voicemail. The reason you may be hearing dead air is because of a compatibility issue. You should post the model and software of your ksu for us to be sure.
Also AA greetings are for incomming calls only. Auto attendant answers inward calls and directs them. If your calling ext to ext you should hear the greeting from the personal mailbox of the extension that did not answer the call.
Hope that helps.
Kevin