Hey @elmoboy
To add to what @KAPABLE-K said, if the WiFi Calling was never set up on your device, you probably have to do it first.
The steps are:
1. Select the Phone icon from the Samsung homepage.
2. Select More (from the upper right corner of the screen).
3. Select Settings.
4. Scroll to the bottom of the page
5. Select Wi-Fi Calling.
6. Select the registration link to begin the Wi-Fi Calling set-up.
7. Enter your wireless phone number in the Wireless Phone Number field to verify your account.
8. Select Get Verification Code.
9. Enter the verification code received by SMS in the Please Enter the Verification Code box.
10. Select Submit.
11. Select Agree to accept the Terms & Conditions.
12. Enter your 9-1-1 Emergency Address.
13. Select Continue to move to the next step.
14. Select Use this Address to choose the 9-1-1 Emergency Address that you prefer.
15. Close the confirmation screen and return to your device to continue setting up Wi-Fi Calling.
16. Toggle Wi-Fi Calling ON from the Wi-Fi Calling screen on your device
This would be the way to set it up while connected to a WiFi. If you are on your mobile data, it might skip some steps 
Give it a try and keep us informed.
@elmoboy If you go to your phone settings and turn on WiFi calling and go through the activation process the quick toggle should work to turn it on/off. You should also be connected to a WiFi network when doing it.
WiFi calling is only available on compatible phones purchased directly from Fido, It will not work on unlocked non-Fido phones.
If your phone is from Fido and you are having problems activating the feature it could be that it needs to be enable on your account, you can contact customer service and they can assist you or a moderator here can assist you.
For more details on WiFi calling see here.
