Wifi calling was never available for oneplus device in Koodo network though. I wondered how you used it previously. Was it only showing up as a setting or you actually used it on WiFi?

I am not sure if this method still works, but you may want to give it a try. Make sure to back up your phone before going ahead with the process. https://community.oneplus.com/thread/1284987

The other thing you might need to do is set/update your e911 address.  More details here: 

@Dinh , yes it was working recently my OnePlus 9 5G ,  bought from Amazon , it was working till i applied the latest security patch , I found its security bug that prevent VOLTE Service 

@Dinh , yes it was working recently my OnePlus 9 5G ,  bought from Amazon , it was working till i applied the latest security patch , I found its security bug that prevent VOLTE Service 

Its already setted thank you . I guess its different issue then 

The security patch was delivered by OnePlus. As the device wasn't a Koodo device, it wasn't pushed by Koodo. 

Anyway, not sure how you made it work. I don't recommend you use side loading customized firmware for security reasons.