I had a brutal time getting straight talk to work with my 520. Here are my settings.
http://i43.photobucket.com/albums/e397/Tehmiz/wp_ss_20140606_0003_zpse87e1255.png
http://i43.photobucket.com/albums/e397/Tehmiz/wp_ss_20140606_0004_zpsea2c854b.png
http://i43.photobucket.com/albums/e397/Tehmiz/wp_ss_20140606_0005_zps6122cccf.png
http://i43.photobucket.com/albums/e397/Tehmiz/wp_ss_20140606_0002_zps96486352.png