You can change the Interdigit Timer Master Override I do not know how to get to that (as I never used the phone).
Looking at the admin guide, the ParName is Interdigit_Long_Timer and the default is 10 seconds. I suggest moving this to 3 seconds.
Now what does that do...... how this work is as follows?
When you dial a number the phone sits there and waits for more input, if no input is provided after 10 seconds it assumes you finished entering the number. So it will convert the digits entered into the DTMF and goes from there.
There is a catch, there always is, if you have people that are