Some users have installed Fast Talkie thinking it is a PTT app. Fast Talkie is actually a lock screen replacement that allows you to quickly control another PTT App like Zello or VoicePing.
If you had accidentally installed it, maybe uninstalling it might not be as straight forward as other apps. This is due to the "Device Administrator" permission required for Fast Talkie to work. To help you uninstall Fast Talkie, here are a few methods to uninstall Fast Talkie. There are a few methods as no one method work on every Android Phone.
Method 1: Go to Settings -> Apps -> Fast Talkie and then Press [Uninstall]
Method 2: Settings -> Security -> Deactivate Device Administrator first, then proceed with normal uninstall.
Method 3: Method 3: Uninstall Via Device Administrator
Video of all 3 methods