I was able to add a pause to the voicemail number on my Android phones but can't seem to find a way on my Lumia 735.
Try adding a comma after the password. Usually this puts a pause in for an amount of time set by the carrier. I think the norm is about 5 seconds. You might have to experiment and add multiple commas.
I tried adding a "p" but it disappears when I close the page and reopen it. What screen should I be on to do this or should I be adding a comma instead? Thanks.