My DNS allows to change your mobile/wifi DNS without root by routing your traffic through a local VPN.
It also comes also with an handy network speed meter icon on status bar for devices with Android 6.0+

Why it's not free and how it differs from other DNS changers?

My DNS, like similar apps, needs to run in background the whole time so it's imperative to be efficient.
It's also imperative to be as transparent as possible since it runs a VPN service on your phone.

For a coffee price you get:

An extremely fast and efficent app with ~ 50kb apk size and less than 5mb of ram usage.
No shady permissions, no internet permission, your data is routed locally only. Nothing leave your device.

There's zero battery comsumption, zero data usage.
There are no ADS, there's no data collection, reports or statistics.
No compatibility issues with Play Store.
Install and forget.