If your device is still on Android 9 (Go Edition), you must manually check for the update. Infinix does not guarantee updates for all variants due to hardware limitations (1GB RAM variants may not receive the update at all).
To see if an official update is available for your specific region and model, follow these steps: Open Settings . Scroll down and select System . Tap on System Update . Select Online Update and then Check for Update . Important Considerations infinix smart 4 update android 10
Here's a brief report on the Infinix Smart 4's Android 10 update: If your device is still on Android 9