I have a one plus 6T from India. When I got a Fido sim, I was not able to make any calls with the same when I chose my preferred network settings as 2G/3G/4G (automatic). However once I manually change it to 2G, I can make calls but not able to access the internet.
Hoping to resolve this issue soon. If anybody has any input, please let me know.
Welcome to the community!
To clarify, are you able to use data when your network setting is set to 2G/3G/4G (automatic)? According to the specifications here, that device should have compatible bands/frequences. You can verify the compatible bands/frequencies here.
While the phone should work on the networks, you should note that since the device is not one available from Fido, it's likely certain features (ie voLTE and/or Wifi-calling) are not supported and will not work with that device. If that is the case, the phone would need to fall-back to the 3G or 2G networks for calls. You might consider disabling any voLTE or HD calling settings in your phone to see if that resolves your issue.
Hope this helps 😀