Cannot Send DTMF Through OOH323 Trunk

Good day!

I have an OOH323 trunk connected to Avaya with dtmfmode=inband. I need to call an Avaya IVR that gives a dial tone and then dial a number to it. Calling the IVR and dialing a number works using a Linksys IP phone with dtmfmode set to inband. I can successfully send DMTF through the OOH323 trunk but not when using softphones like X-Lite and Ekiga. In addition to that, I need to automate the process, so I need the Asterisk console or a custom extension to automatically dial the numbers by sending DTMF. Unfortunately I cannot send DTMF using the dialplan. In summary I cannot send DTMF using the following methods:

1. SendDTMF()
2. D() option in Dial()
3. Dialing using Softphones like X-Lite and Ekiga

i. SendDTMF()
Using .call file, I initiated a call between an Avaya IVR and an Asterisk custom extension that sends the number to the IVR. The Asterisk custom extension sends the DTMF using the code below.

exten => s,n,SendDTMF(${Num})

I also tried initiating a call to an Avaya instead of an Avaya IVR so that I could listen to the DTMF but I did not hear the DTMF.

ii. D() option in Dial()
I created a custom extension that the Asterisk console can call and have it call the Avaya IVR and send the DMTF for it but it wasn't successful as well.

exten => 123,n,Dial(OOH323/${IVR}@X.X.X.X:1720,10,gD(${Num}))

Again, I also tried calling an Avaya extension instead of an IVR to listen to eat and there's nothing.

iii. Dialing using Softphones like X-Lite and Ekiga
As I have mentioned earlier, I can call and send DTMF to an Avaya IVR or extension using a Linksys IP phone but not when using softphone like X-Lite and Ekiga.

The part where DTMF should be sent in the h323_log show DTMF captured as null.
h323_log:

14:27:03:440              elem[2] = {
14:27:03:440                 capabilityTableEntryNumber = {
14:27:03:442                    3
14:27:03:442                 }
14:27:03:443                 capability = {
14:27:03:443                    receiveAndTransmitUserInputCapability = {
14:27:03:444                       dtmf = {
14:27:03:445                          NULL
14:27:03:445                       }
14:27:03:446                    }
14:27:03:447                 }
14:27:03:447              }
14:27:03:447           }

Is there a way where I could set the dtmfmode of the dialplan, the console and the softphones the same way a Linksys IP phone can set its dtmfmode to inband because in my setup now, it's the only way I can send DTMF through the OOH323 trunk. The dmtfmode in the extension configuration in sip.conf for the softphones does not work. The extension that I use for the Linksys IP phone has dtmfmode set to rfc2833 in sip.conf but still works as long as the dtmfmode in the main device's configuration is set to inband. I guess what matters is the dtmfmode set in the device. So that's what I need now, set the console or dialplan's dtmfmode to inband.

Please help me. :)