Woah! Already on your second S9+? Gosh, that's rough seeing how it just got released. When you upgraded your phone did you also get a new SIM card? Have you tried using your SIM in a known working device to see if you still have the delay in sending texts?
Hi braddman - I've had one or two texts fail, but mostly they are successful. Do you know what your signal strength is when the SMS fail?
@tmo_amanda has a good point, I've see a few bad SIM's cause issues like that. Your S9+ should have come with a new SIM in the box...are you using your old one or the new one. Maybe a call to support, they can swap the SIM and see if it helps!