Someone used to sell an RS232 to LAN adaptor that worked with Stratagy. You could try one, but sometimes the voicemail system is a bit touchy. I have had USB serial adaptors that gave me troubles connecting to the voicemail system.

As far as dialup, if you have an analog port on the CIX, then you could use dialup to the voicemail by dialing the voicemail extension. I have done that in a pinch when my serial cable didn't work, or it got left behind. It's pretty slow, but it will work.