Unhappy [Q] ringtone problem

i have alcatel scribe easy run original room without root android 4.1.2
i have a problem in setting mp3 as a ringtone that when i restart the device it return to the default ringtone that is only when i insert the external sd card when i restart the device the mp3 disappear from setting ringtones list and show only the default ringtones but when i remove the sd card the problem gone and every thing is ok after restart and restart but when i put the sd card again it come gain the same problem i tried every thing from using app like mp3cut zedge and also tried t put the mp3 on the phone storage ringtone folder and on sd card on ringtone or even media-ringtone or audio folder still the same i think it's a problem in setting the default storage when it have no sd card it's no problem but when i put the sd card it become the default storage even if i set the default storage to phone after restarting it become again sd card is the default storage any help and sorry for my bad english