I fixed echo problem on my iphone 11

Resetting network settings resets all data connections back to the out of the box factory defaults.

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To perform a Network reset, follow these steps.

1. From the Home screen, tap Settings > General > Reset.
2. Tap Reset Network Settings.
3. Type in the device password if prompted.
4. Confirm selection.

This does not change any of your personal information. It worked great for me!