I have generated custom ring tones and stored them in the phones internal storage. I have gone into Contacts and redirected the desired peoples ring tone to the one I want to assign to the person. Everything looks good and the redirected ringtone name appears in the data for the assigned persons. The problem is that when a call comes in from the assigned person I get the default ring tone not the assigned ring tone. Since the correct ring tone name shows for the individual why do I not get this ring tone?
I am not sure if that would be a software glitch or more of the phone is unable to determine the caller until it has already received the signal for an incoming call so it gives the default sound instead of the personal one. For a software glitch, you can simply backup everything and do a factory reset. You may want to reach out to your service provider and speak with upper level tech support regarding the other theory.
If it were the issue that the phone is unable to determine the caller ID then it would not work intermittenly. It has worked fine on other phones that I have used. I bought a factory unlocked phone and would expect Samsung to have a straight answer, especially since it does not seem to be unique to my phone.