iPhone 4 Ringtone not showing up

I bought a text tone from iTunes that says “you’ve got a text message.”
In assigning it to a contact as a text tone for that contact, it will not show up. It only shows up when I try to assign it as a ringtone for that contact. But that is weird as when my phone rings for a call, it would say youve hot a text message. How do I assign it as a text tone? I tapped the contact then tapped edit. Tapped text tone. I don’t see the purchased tone.
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Cyrus Dubash