Sounds like you might have misunderstood what you need to do. There is normally nothing related with DTMF that you configure on the phones. Can you please give a description on the situation you have and especially any problem that you face in as much details as possible?
That's not a setting that you would normally ever touch. We have thousands of phones and none of them have this set. All of them can make calls to internal and external parties.
Please describe the problem you have and I'm sure we'll be able to help you out.
There are DTMF settings that can be set on trunks. For us to be able to help you out you need to give a little information on how your IVR is integrated with CUCM. We are not familiar with your specific system landscape and can not really give you much valuable advice with the sparse information you give so far.
So your IVR system DTMF is working on in-band and not via the Named Telephone Event (NTE) system.
if you provide the details how its integrated with CUCM, we can see the best option to turn on.
At the very bottom of the trunk configuration in the CUCM there is a setting for DTMF. Try different settings and reset the trunk after each change you do before you test again.
Can you apply MTP on MRGL and apply it on the phone device pool and see if it works.
If you prefer to use Require DTMF Reception and want to activate it on all phones this can be achieved using Bulk Update Phones.
Or as @Roger Kallberg mentioned You can try changing the on IVR trunk. You need to consider the MTP when changing the DTMF and below document explains when to use MTP.
