Go into your phone's Settings >> Apps menu, find and open the Phone Cleaner Pro app entry, tap on the 'Force stop' button, then find and tap on the 'Clear data' button, then tap on 'Uninstall'. Using Clear data will remove all the user data and config files for the app, along with its cache -- If you use just Uninstall, it will remove the app data but not necessarily all the app's related files.