Normally the system should be able to add it for you automatically. Are you having Koodo cellular signal as of now and you have data ON?

I have koodo signal and data On, I think the problem is the VoLTE add-on is not included in my plan

That was weird, let me flag a rep to look into it.

I assume you are  a postpaid customer?

Yes. I’m a postpaid customer. Thank you!

Hi ​@WarrentW, the VoLTE add-on has not been necessary for some time, the service is just active for all eligible phones. You can see the service on your other line as it was activated before this took effect. 

This is the same for the VoLTE switch in your phone settings, it has been removed and the service is active by default.

Here is a guide to activating Wi-Fi calling in your phone https://www.koodomobile.com/en/help/wifi-calling

Hi, I can set wifi calling on the other line that have VoLTE add-on. but when I set wifi calling on this one it always say “ to allow wi-fi calling on this account, contact Koodo.” I don’t know why. 

Thank you. I restarted my phone . it worked.