Heres one solution I found,

To assign individual ring tones:

1) you must go to the phone book, highlight the wanted contact, click on options and then edit.
2) scroll down until you see the section "ringtone" and click on it.
3) Then choose audio, then ringtones. click on the ringtone you want, you must listen to it first, and then click on "select".
4) if you want a ringtone to be something you've recorded, click on "my voice" rather than "ringtones"

let me know how that goes.
Thanks,
Ekse

Hi
i have made a detailed research on your queary,but unfortunately in this specific model u cant assign specific ringtones tho the general method of assignin specific ringtoes is the steps below,u can give it a try,jus tellin u so tht u don get upset wth your phone,cheers..!
To assign individual ring tones:

1) you must go to the phone book, highlight the wanted contact, click on options and then edit.
2) scroll down until you see the section "ringtone" and click on it.
3) Then choose audio, then ringtones. click on the ringtone you want, you must listen to it first, and then click on "select".
regards