The "message" part of the greeting could refer to a voice message. Some pager services notify users that a voice message is available, and the recipient calls calls into the service provider with a PIN to retrieve the message -- other services have a person (or voice recognition software) transcribe the voice message to text which is forwarded directly to the pager. As far a sending text directly to a pager, there is often an e-mail address associated with a pager for short messages (e.g., the default address for Skytel pagers was {10-digit_pager_number}@skytel.com).