Hi there - for the ones that don't go through, do they show as sent on your phone? The people that you're sending to, have they by chance said that they experience this problem with others as well? Lastly, have you tried removing/reinserting your SIM card and rebooting your phone?
Hello, my LG G4 does not send text mesages to my contacts. My contacts have never experienced throubles receiving texts. I loged in my koodo account and it shows my activity, my texts sent although my contacts do not received any.