asterisk users - Jan 2014 - Cisco SPA504G, transfer asterisk page()

exten => 179,1,SIPAddHeader(Call-Info:\;answer-after=0)
         exten => 179,2,Page(SIP/180&SIP/181&SIP/182&SIP/184)

The asterisk11 page() application works great, but I've just learned 
that the person who initiated the page can transfer or conference the 
page if they don't hang it up before using those functions.  It never 
would have occurred to me to try it, but a user did it accidentally 
today and it caused quite a stir when somebody's conversation with a 
caller was being broadcast from every phone.

They're using the conf and xfer buttons on the phone to make this 
happen, so I'm not sure if asterisk can even prevent them from doing it 
or if I have to figure out a way to stop it from happening on the 
phone.  The "i" option for Page didn't help.

Anybody dealt with this before?