In a particular embodiment, a disconnect message with a progress indicator may be received in a PSTN protocol at a gateway. The gateway determines if the disconnect message includes a progress indicator. The gateway then generates a SIP message with a reason indicator that indicates the SIP message is mapped from a disconnect message that includes the progress indicator. The SIP message is then sent to a second gateway. The second gateway determines that the SIP message should be interworked to a disconnect message. The second gateway uses the reason indicator in the SIP message to determine this. Accordingly, the second gateway sends a disconnect with progress indicator to a second PBX. This allows the second PBX the option to either listen to an in-band announcement or to disconnect without listening to the in-band announcement.