ZenFone 6 will not make or receive calls

My ZenFone 6 (AT&T USA) will not make or receive calls. Texts work fine. The phone updated to Android 10 last week and I was able to make calls. I turned wifi off and was able to make one call but now it doesn't call or get calls no matter what I do.
I restarted the phone multiple times and reset wifi,mobile,& bluetooth via Reset options, this did nothing.
The phone is not in Airplane mode.
Firmware version is: 17.1810.2009.176
The phone is not rooted
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Comments
It's me or Zenfone is not really well established in USA's cellular networks ? 🧐
My son's LG phone on the same AT&T plan works fine so I know it's not the network. Any ideas what to try Tech Support?
yes ZenFone 6 Itself a Big Problem, ASUS Cant Solve any problem. My problem about Network is also not solved but they created more problems in mobile... WTF... Asus.
I think it's a BIT absolutistic.
They can't solve this problem not ANY problems.
Did you tried a FACTORY reset of the phone? No other complains about this so it seems to be a problem just with your phone. A reset may solve. Otherwise maybe an hardware problem.
Started working correctly again out of the blue, 20+ hours of not being able to make or receive calls then poof it works again... so strange.
If it stops working again, then please factory reset and if no improvement, contact your local support.
Thanks!
No need to project the service issues you've had in other threads with different issues. We know about your situation and we will solve it. Just talk to ARP_ASUS and I'm sure you will work it out.
Thank you for your understanding