I would suggest you to try changing your APN settings according to the following link listed below. https://forums.oneplus.com/threads/mobile-data-not-working-on-telus-after-android-11-beta-update.1474006/#post-23495294

Make sure to keep your SIM card inserted into the device until you try to access the APN settings. Once you are in the menu, quickly open the SIM slot. It would be preferable to add another setting instead of using the default one. Once that is complete, save the settings and restart your phone to update it. Your service should be restored. 

Hi,

So the issue is resolved now. I had to go get a new sim card and then I used APN settings listed on Koodo website : https://www.koodomobile.com/en/help/setting-data-your-non-koodo-phone

My phone did allow me to save APN settings etc without removing sim card.

I would suggest to anyone who has tried Koodo’s APN settings with no success that they should perhaps get a new SIM card.  I went to a koodo store and I got a new sim card for free as mobile data wasn’t working, changed the sim number online (self serve > mobile services options), new sim card activated right away, double checked APN settings and everything was back up and running.

Thanks to all those who responded. 

I hope this helps.

This is what worked for me:

Go in the apn settings. Delete ALL APNs entries. I had two myself.

After that you should see radio buttons with sp.koodo.com entry. Just choose it and should work immediately.

Seems there’s a myriad of ways to resolve this issue. It should be noted that the APN diagram is incomplete for non-Koodo phones. The diagram works for phones purchased through Koodo because the APN is programmed into the phone.

APN Settings | Koodo

For non-Koodo phones the APN will, in most cases, have to be edited. The two fields that are missing in that diagram are MVNO type and MVNO value. If you’re just going by that diagram, you won’t see the two missing fields which results in an APN that cannot be saved. The MVNO type is the only field to be concerned with as the MVNO value will auto-populate once the type is set.

Koodo APN Settings for OnePlus 6T - scroll down to MVNO type & value.

The MVNO type used in a previous solution was IMSI. However, Koodo uses GID. Setting the type is simple. Many say they have access to the APN, so it’s just a matter of tapping on MVNO type and selecting GID from the dropdown menu. Remember to save your edits to the APN.

Thank you, you’re the Best. 
Since the release on Oct 2nd, I’ve called koodo, spent over 1:30 mns; I went to 4 different koodo locations, to no avail. One even tried to sell me more data and a new phone.

Kudos to you :-)