If not, I'll leave the more technical solutions to the more technical members.
Settings > Galaxy Beta Programme > Deregister.
Try re-install the old software version by using the PC version of Smart Switch. Once the software is re-installed, the device will be reset and all data that was generated during the Beta Program will be erased.
What is the model number of your device? Is there any error message while making or receiving the phone calls?
you can Reset Network Settings and check. Follow the below steps:
Go to Settings >> General Management >> Reset >> Reset Network Settings >> Reset settings.
You can try wiping the cache partition of your device and check.
Also, As mentioned by JohnH, as of now beta testing is not available for Canadian samsung devices.
If you are using the US version phone, please contact the Samsung US community forum as mentioned by Cprice. As of now, beta testing is not available for Canadian Samsung devices.
Thanks to Cprice and CHMultimedia for your inform
But there's no beta for the N20U yet. Did you flash the S20U firmware? Or do you have a S20U?
Gosh, I should probably make my tutorials to avoid people from making this mistake