DTMF is Not working in VOICEMAIL

Hi everybody,
I have linksys phone at my location,
i am using asterisk version 1.4.19,
I have a issue regarding dtmf mode, i have set the Asterisk DTMFmode to Auto in order to eliminate Asterisk effect on the DTMF transmission. Both Inband and AVT from Linksys worked with PSTN IVR.
But, We have the issue why Asterisk Voicemail doesn’t work with Linksys set to Inband and Asterisk set to Auto. :question:

Anyone please help me for this issue, i have searched many pages but i haven’t found the exact solution or reason for this? :cry: