To those who were a little confused with what I wrote:
Basically you want the voice prompt to stop when a user starts entering key presses. This can only be done by moving to a new OGM without a voice prompt. The way I explained is that your OGM system would take the first digit of the input and then move to this new OGM to receive the rest of the input.
So say your desired input is 10 digits long. You would create a system with two OGMs. The first OGM asks the caller to type in their 10 digit number. When this OGM receives the first digit of this number it then saves this and moves to the second OGM. This second OGM does not have a prompt but simply waits for the other 9 digits. You would then have your 10 digit number split up over two variables in IVM.
I'm sorry if this is still confusing, but it is a complicated process. An alternative solution is to make your callers "Press one and then enter in your 10 digit number". This allows your 10 digit number to be stored in the one variable, but requires that extra key press which your callers may forget.