Hello and thanks for reaching out!
Have you tried using this method? http://bit.ly/JxHDOd
Also make sure these files are actually in the appropriate file format. As long as the music player can play the file, you can use it as a ringtone.
Try adding these files as music and then setting them as ringtones using the method linked above.
If you need additional assistance please contact us again. You can also reach out to us via twitter or facebook for quicker responses.
Thank you and have a great day!
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