Settings -> General -> About -> Carrier -> Rogers 28.4
My iPhone 6 Plus is unlocked, I bought it outright from Apple in September 2014.
I did not have to call Rogers. But I used to have a Rogers One Number subscription and, until they cancelled that service, I could not activate Wi-Fi calling. As soon as Rogers One Number was cancelled on 31 January 2017, I was able to turn on Wi-Fi calling.
Problem solved. I am posting for others who may have the same problem.
They had to delete the SOC code on my account from a previous try (issue with Canada post address for 911). They can't manually put it in the SOC code so I had to generate it again. It asked me to register my address again and this time it was done correctly. Received the email below to confirm.
Thank you for signing up for Wi-Fi Calling. Now, you can make and receive voice calls, SMS and MMS messages on your device over any Wi-Fi Connection. A copy of the current Wi-Fi Calling Terms and Conditions are attached for your reference. If you have any questions or would like to learn more about Wi-Fi Calling, please visit rogers.com/wifiCallingFAQ