Asterisk + IAX2 + ChanSpy 1 way audio problem

Hello, i’m experiencing some problems with ChanSpy and IAX2 extension, i only hear the incoming audio, and nothing from the extension that are calling.

Mi config is IAX2 extension to Asterisk and a SIP trunk to outside, everithing en ulaw codec.

Here is mi extension.conf

exten => _*666.,1,ChanSpy(IAX2/${EXTEN:4})
exten => _*666.,n,Hangup

any clues?