I am in Ontario,  and for some reason,  that will happen to me once in a while.  I'll send a text, and the next time I look at my phone, I'll see that it says message not sent. I usually just reboot my phone, and then hit the message not sent and eventually it sends

Thanks! It didn't work. But one thing I noticed is my friends with Virgin and Bell are getting my texts so far .

Ah ok. I took it to  Koodo . And it boils down to the fact that it's an LG . Lol

I have a Samsung....so nope.... it's not because it's an LG. Although LG is no longer updating their operating system.  So you may want to switch to a different phone manufacturer 

So I put my sim into a working Samsung S9 Plus. And the same problem occured. 

Maybe it's a SIM card problem?

Maybe.  Just go to a koodo or telus store and maybe they can help you.  Good luck