Multiple years experience working for cell carriers - know everything about plans, devices, customer service,...
Go to Settings->General->Reset->Reset Network settings. Let it reboot and then wait for a few minutes until the signal bars come back and it says Sprint and 3G up in the top left. If that still doesn't work, take it back to the Sprint store.
All sprint issues
The secret to getting the web working agin if the above does not fix it, call sprint tech support, u pull ur battery, sprint rep refreshes the signal to ur phone, u replace the battery, and try the web, wala...it has web. U lost web bcs something interferred on the network & ur signal got dropped.