Please check the relevant section of our documentation for each SDK and you can find out how to switch cameras on a device:
iOS SDK - Advanced | Video Calling | iOS SDK | QuickBlox
Android SDK - Advanced | Video Calling | Android SDK | QuickBlox
React Native SDK - Advanced | Video Calling | React Native SDK | QuickBlox
Feel free to check our official documentation for more information that will help you to integrate QuickBlox services into your applications / projects or contact our Support team by submitting a ticket if you have any other questions.