If you have jailbroken device you can customize the UI of Phone app in iOS 10 with new Cydia tweak installed. Dubbed as Phone Tools this jailbreak tweak by Justin Petkovic allows you to customize your Phone app’s user interface by disabling or removing the features you don't really use.
There are many tweaks in Cydia that offers similar functionality for apps like Camera and Photos, but this is the first tweak that is developed to work on the Phone app in iOS 10.
Phone Tools is available as a free package for download from Cydia’s BigBoss repo. The tweak supports jailbroken iOS 9 and iOS 10 devices and is designed to work only on iPhones.
So once you install Phone Tools tweak, navigate to the Settings app where you will find a new preferences pane to manage all of your settings. Once you're done with settings hit the Respring button at the bottom of the preferences pane to save your changes.
Phone Tools tweak really offers many options to customize the UI of Phone app in iOS 10. Those users who have no SIM card or use their older iPhone simply as a Wi-Fi communications device really can remove the Voicemail tab, for instance. You can also use additional options for filtering third-party app clutter from the Phone app, if you don’t want to see all of their important phone calls getting mixed into the bunch with a ton of history items from other apps that may not be as important for you.
As for me Phone Tools is a simple tweak that many users will love. So if you want to customize the UI of Phone app Phone Tools will definitely help you to do it on your jailbroken iOS 10 iPhone.