To do that, you would need to be rooted with a custom rom. You might also need a theme with that rom. As of now, there are no roms for your phone, nor is there an official root method. However, that could change at any time. Meanwhile, you might want to check the All Things Root forum from time to time for updates:
http://androidforums.com/optimus-g-pro-all-things-root/.
You could also do a search for dialer apps, as El Presidente suggested, in the Google Play store. These may have customizable options that don't require rooting.