'A Call From Your Wife' -- Treo 750's caller announcement could be a bit inconvenient

Got this one in from a Treo user:

I feature has automatically turned itself on on my treo 750. When someone calls me, after the first ring a digital voice then speaks (through the loudspeaker!!) “a call from Ewan” – using the name from my address book. How wicked. But how do I turn the feature on and off? Anybody any ideas? Nobody here seems to know and indeed everyone thought I was joking when I told them about it!!! And what happens when I am with somebody I shouldn’t be and it says “a call from your wife”!!! what fun I am going to have 😉

That’s a pretty nifty feature, although yes, I think it could be rather inappropriate if you’re sat there in an interview and your device screams out ‘A call from Squidgy Pie’. Heh. Anyone know how to turn off the feature? I’m sure it’ll be a little checkbox someone on the OS.