the u520 only accepts .mid ringtones unless you use bitpim to go in and edit the brew folder where ringtones are saved it will play mp3 songs but not as ringtones sorry for ya luck pal

Samsungs dont allow this to happen just like they wont allow you to transfer files between you and another bluetooth device bc of the DRM * Digital Rights Management * Pretty much copyright protection . most companys rather not have to worry about people infringing on anything that is copyrighted . Verizon / Sprint for a example have the DRM function on all there phones not just samsung models