Remove non-existent devices from "Calls on Other Devices" on iOS?
I had an iMac showing twice within &quot;Calls on other Devices&quot; on an iPhone
The following got it fixed for me.

Removed my iMac from the iCloud account
Logged into iCloud again on the iMac
Logged in FaceTime on the iMac
Switched off/on &quot;Calls on other Devices&quot; on the iPhone

Hope this helps