DTMF remove (cut)

I do not want to passthrough INBAND dtmf.

How remove (cut) them or may be disable passthrough ?

I found function VOLUME
wiki.asterisk.org/wiki/display/ … ion_VOLUME

Arguments
direction - Must be TX or RX.
options
p - Enable DTMF volume control

But this not work as expected :
$AGI->set_variable(“VOLUME(RX,p)”, “-200”);
$AGI->set_variable(“VOLUME(TX,p)”, “-200”);