Sprint may have horrendous coverage in your particular location on LINY (you can check their
coverage map to see what it should be in theory) and if so
it's possible to get Airave from them for free to retain you as a customer. As for the person at the store blaming your problem on Windows Mobile, lame responses (and lame reps) can be found at any carrier. Unless it's a repair store where I have an established track record with their techs, I'd just as soon phone in a problem like that to Sprint tech support. Also, system glitches can occasionally occur that cause problems like you're experiencing. I experienced several undelivered text messages a few weeks back. But it was very temporary, and that kind of thing is rare in all the years I've used Sprint.