Welcome to the Community.
Sad to see you're having complications with this feature. Can you tell us if you get an error message when you try to send out a text message?
Can you also confirm that you're using the text messaging App that came with the phone? Which device are you using?
There is not an error message when i am sending sms and i can confirm that i am using the text messaging app from the phone. I ve checked sms settings and SMSC number is +15149931123. The device is One Plus 6T, its a new device bought 5 days ago.