When my phone arrived brand new from Samsung direct it had only a beep for a ringtone. So I managed after a lot of research to download a music file and install it. Since then, every time that there is any sort of system update, the beep replaces tbe music file. I have until now been able to reinstate it, but after the update a week back, the beep has returned and looks like it's permanent.
It's not going to be a problem as I intend to bin this phone after getting a Motorola.to replace it. However it would be good to know how to install this music file as my ringtone so that I get a working phone in the meantime.