asterisk users - Sep 2013 - Function CDR_PROP

In Asterisk 12, how should I call the function CDR_PROP
"set(CDR_PROP(disable)=true)"
or simply CDR_PROP(disable)
I am getting two records per call attempt, and I cannot figure out how
to go back to get only one record. So far I am using this technique,
but it changes nothing. My calls always involve a single caller a
single calee

exten => 100,1,NoOp()
 same =>     n,Dial(SIP/bob,,b(default^callee_handler^1))
 same =>     n,Hangup()

exten => callee_handler,1,NoOp()
 same =>                n,Set(CDR_PROP(disable)=true)
 same =>                n,Return()


Philip