No service no cellular connection searching for service

If you see No Service or Searching on your iPhone or iPad

1. Check your coverage area. Make sure that you're in an area with cellular network coverage. ... 
2. Restart your iPhone or iPad. Restart your device. ... 
3. Check for a Carrier Settings update. ... 
4. Take out the SIM card. ... 
5. Reset your Network Settings. ... 
6. Update your iPhone or iPad. ... 
7. Contact your carrier. ... 
8. Get more help.

If you see No Service or Searching on your iPhone or iPad ...

Yep same issue, since Jan. 10th after I did latest update. After 15 calls to T-Mobile and a store visit they finally concluded it was my iPhone 8+. I tried EVERY online trick 20 times nothing worked (Everything that SranvanKrA suggested). Finally got the idea to put sim card in my old iPhone 6 and that phone works fine. I just tried a factory reset and that did not work either. Can't believe Apple is not coming forward and at least acknowledging the problem, I really don't like putting my life in danger going to stores during a pandemic to try and fix an issue they know about, but will not acknowledge yet.