There is currently a Sprint Nationwide Outage, we were just informed, and Sprint is currently working to resolve this issue at this time. We have no estimated time of repair.
Have you contacted Sprint about this issue? Have them check there coverage map to see what coverage your getting? You may be eligible to get an Airwave.
The Texting Error Code 2128 should have been fixed it was Nationwide Outage. Have you tried doing a Profile or PRL Update on your Device through your settings?