[overhead]
exten => s,1,Background(oh-record)
exten => s,2,Record(page:gsm|3)
exten => s,3,Background(oh-isthisgood)
exten => 1,1,agi(page.agi)
exten => 1,2,Hangup
exten => 2,1,goto(overhead,s,1)
exten => t,1,Hangup
exten => i,1,Playback(pbx-invalid)
exten => i,2,goto(overhead,s,1)


[playpage]
exten => s,1,Wait(2)
exten => s,2,Playback(page)
exten => s,3,Hangup


pgrace@astpbx1:/var/lib/asterisk/agi-bin$ cat page.agi
#!/bin/sh
echo -e "\
Channel: SIP/3000\n\
MaxRetries: 2\n\
# Retry in 5 min\n\
RetryTime: 300\n\
WaitTime: 45\n\
Context: playpage\n\
Extension: s\n\
Priority: 1\n\
" > /var/spool/asterisk/outgoing/page