Back in May 2017, Apple filed a patent application for a way to communicate with Siri by writing her questions and responses using iMessage. While that didn't make it into iOS, thankfully, something even better did — a way to ask Siri things with the keyboard directly in the Siri interface. This works in iOS 11, iOS 12, and iOS 13, and it will likely continue to work for future iOS versions.
If you like having Siri available to answer a quick question every now and again but don't want everyone who picks up your iPhone to also have access to your personal assistant, there's an easy way to disable her from working on your iPhone's lock screen. This is also something you can do if you're always activating Siri accidentally in your pocket.
Siri makes it easy to call almost any contact on your iPhone with just a quick verbal command. I say almost because counterintuitive name pronunciations such as Caoimhe, which is actually pronounced "Keeva," will confuse the hell out of Siri. Luckily, there's a way to get Siri to understand pronunciations for the tricky names in your contact list ... it just takes a little grunt work on your part.