DTMF detection problem in PABX trunk

Hi for all,

i 've installed asterisk with isdn trunk with alcatel pabx.
When alcatel users dial for external numbers, a channel on asterisk is allocated for dial. When we call to an number that is an IVR the digits isn’t recognized by IVR.

In sip.conf i putted dtmfmode as rfc… and info, inband is only for 64k codecs, and still don’t work.

How can i resolve this issue ??