default ringtone keeps changing to mp3 topic

I just signed up with Verizon and got the sgs5 running 4.4.4 kitkat. I change the default ringtone in settings>sounds or in the phone app in settings>call>...and it keeps it for 3-8 hours then changes it to a song that is on my sd card. Has anyone heard of this before? I have been working with Samsung to no avail. I suppose I could take the sd card out and see what happens. I did install a new sms messaging app...Textra. I guess I could uninstall and see if that changes things but wondered if that wasn't the reason. Thanks