Anyone added a day to a ticket over the phone recently?

[abnihon]

I have linked tickets from UT and if MK ends up staying open late on our arrival day we may want to add a day to our tickets so we can go on arrival day.
Will Disney let me add it over the phone so I can make park pass reservations?
I’ve read mixed things about them sometimes only allowing it at guest relations but that was all pre-park reservation info.