CarPlay Echo
I have a 2020 Toyota Rav4 and when I am talking to someone using Apple CarPlay the person on the call can hear their voice echoing back at them. I found this same topic a few years ago with the steps below to fix the problem; however, there is no option to change the option Voice and Data to just Data in the Enable LTE screen.
I have the most up to date firmware on the car and the latest IOS.
Go to settings
Go to Cellular
Go to Cellular Data options
Go to Enable LTE
Change option from Voice and Data to just Data
This removes the ability to operate internet while talking, but the echo goes away.
Found the solution on this article. https://discussions.apple.com/thread/7697280