step 1, (from someone on Reddit)
Dial *#2263#, select NR5G Band Preference, then select NSA only. Select GO MAIN, and finally apply band configuration. It should say Apply DONE, press the home or back button, and you are good
Step 2: (figured this on my own, if you are still having issues)
reboot after step 1. do the same thing as above EXCEPT in the NR5G menu select the first option, and apply and reboot.
last option but do above first (if you are on tmobile), go to the store and ask for a R15 SIM card. tell them you are having data issues. tell them support said you needed one and leave it at that, they should give you a free SIM.
Thank you for your feedback. Network connectivity issues will most likely be resolved more effectively by contacting your carrier directly. If issues, persist, however, please send us an error report to help us debug the issue. Please also keep an eye out for any other issues you may encounter. We apologize for the inconvenience and appreciate your contribution to the beta program.
One UI Beta Team.