"tmobile diagnostics keeps stopping" galaxy s20 pop-up

Happening on my note 20 ultra. My phone is useless tried contacting service and they told me nothing is wrong. Well when I am giving presentations at work and the app force closes and pauses videos something is wrong. I guess it is time to move my business and my phone to another network that works. Cause TMobile has no answer. What a joke. Yes I have reset cache and data on 12 different phones. Still have the same problem.