is it on your parents account or something? did they setup the phone plan so that texting is disabled?
u need to find another cell phone to test this out. theres gotta be someone u know who u can call and say hey 'send me a text.'
try emailing from a pc to ur phone. it goes throught the sms network.
xxxxxxxxxx@messaging.sprintpcs.com
put ur 10-digit number in where the xxxxxxxxxx's are