I saw someone post on general forums about voice quality. For what reason this isn't set to default i don't know.
What this does is enables and changes your Voice codec(unless its called something else) to EVRC-B.
Requirements: Need your MSL #
To get your MSL # you can either call sprint and play dumb(I say i need to reprogram my phone) or since we have root download MSL Reader off the market.
Step 1: Once you have the MSL # go to you dial pad and press ##3282#.
Step 2: You will get a window that says EPST, hit the Edit Mode. This will prompt you for your password. Type in your MSL number there and hit OK.
Step 3: Now your are in the EPST, Go to the Advanced menu.
Step 4: Scroll down till you see Vocoder. Enable this if it not by pressing on it and slecting enable.
Step 5: Below Vocoder is the EVRC-B, do the same thing if it is not enabled.
Step 6:Next setting is the Home Orig and Roam Orig. You want to change these to EVRC-B.
Step 7: Press your menu button, Commit Modifications will appear. Press it to save the changes. This will automatically reboot your phone.
Once it is back up, people should notice a better call quality from you.
Written pretty shitty huh? lol