I got my new phone a Pantech about 1 month ago. Mine changed on its own, but I had to check it out. I guess it did because I turned it off when I went into church on Sunday morning.
Go to 'Shorcuts" then "Alarm Clock" when that comes up, select "create new" scroll down to "time" hit select. It should come up with the place to change the time. Try it. Hope it helps for next time.
kathyd