There's a menu you just punch in with the keypad. 47*68#13580 <--- That's a menu which you punch in other number's to change settings. You will need to find out the # to reset the phone to COMPLETE Factory Defaults (Everything Cleared, even the phones programming). But WARNING: Do NOT play around in there. You could end up punching in a number, which will make changes to the settings you might not even notice, and a possibility bricking your phone. Straight Talk probably won't tell you the code, but that's my guess.
Phone History: Nokia 2125i (Virgin Mobile), Samsung A645 (Telus Mobility), LG 3300 (Virgin Mobile), Samsung A640 (Virgin Mobile), Samsung M510 (Virgin Mobile), Samsung M300 (Virgin Mobile), Samsung Vice (Bell Mobility), Samsung Impact (Bell Mobility), Samsung Gravity 3 (Bell Mobility), Nokia C3 (Rogers Wireless), LG Neon (Rogers Wireless), Nokia E5 (Rogers Wireless), Samsung Galaxy S II X (Koodo), LG Nexus 5 (Koodo)