Unless the two of you live in the same area, I wouldn't rely on senttoschool's advice. Quality of wireless service is going to vary drastically dependent on your location.
If your relationship success is dependent on SMS, you're doing it wrong.
Nah, it's easier than you think. Imagine your gf wants to see you and tries to call and text but you don't receive any of it. Now imagine this happening frequently. It's definitely an igniter to fights.
Also, I'm not an old fart like many here. We use text to communicate because it's very convenient to check up on each other since we don't live in the same city.
Also, I live in San Francisco and around the Bay Area, the tech capital of the world. You would think sprint can get their act together here.
I used an old ass iphone 3G(second iPhone ever) on AT&T and still had far better internet than sprints lte and much better reception.