I have discovered SettingsExtns by accident today. What is this?
That is a component connected with HD Calling from Verizon. Many users report it as the bloatware, but it's actually a part of the System UI. The only thing you can do is to mute or disable it, but that might have an impact on your device performance and features. I strongly recommend contacting Verizon for further details at https://www.verizonwireless.com/support/contact-us/