Remote Support can be used to allow support personnel to view a user's mobile device. Only the user can control the device, but the support person can see what happens.

Vendor Documentation: Screen Sharing on iOS Devices

The user must change some device settings, then allow a Remote Support session. The vendor documentation covers both parts.

Vendor Documentation: Screen Sharing with Android Devices

For technical support providers, more complete information is available.

Supporting Customers using iOS Devices

Supporting Customers using Android Devices