According to the bottom right of the Operations Manual pg 21, we SHOULD be getting those callouts.

I don't have the CS 727, but perhaps those wav files are buried in the SOUND folder for that aircraft?  Look and see if there are, if you own it, and if so, maybe a little copying to the 707 SOUND folder might fix it.  If it does, let me know.  If this is just a case if missing wav files, that'd be easy to resolve.  Let me know if you have the 727, and if those wave files exist!