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After many many calls to tech help desk I have finally reached the correct person to send out the settings to my Galaxy S20 FE and my wife's Nokia 2.4 which is required to enable the toggle switch to appear under phone settings, and thus enable me to turn on wifi calling on both handsets. My thanks to all previous posters advising that this is the only solution if the toggle switch is not present under phone settings.. Most tech advisors are not aware of this solution, so after going through the usual solutions (text CALLING to 97888 - turning wifi calling off and back on their end) it is extremely hard to persuade them to connect you with a 'back room' tech engineer who will have access to their software tool that can send out the OTA (over the air) provisioning configuration settings to your phone. My thanks to Manoj at Vodaphone for getting me up and running. Whilst on the call the settings were sent to the S20 - there was no notification message, the toggle switch just appeared under phone settings. For the Nokia 2.4 there was a notification message saying 'IMS settings received' clicked on that and then given choice of full or custom install. Clicked on full and a few seconds later the toggle switch appeared. Shared to help the many readers facing this problem, which when you finally get access to the correct back room engineer is a 20min fix.