Is it always in the same location?
I.E. - at home - or at work - or location doesn't matter?
I work in a VERY earthquake proof building, which has reinforcements and
upgraded pillars / steel supports all over the place in the building.
When I am in the building, near the middle, I sometimes have problems sending texts.
I have to move closer to windows and re-send the text, then it will go through.
How's your signal strength?