1) Open the Settings app on your device.
2) Touch Sounds or Sounds & Haptics in the list.
3) Now tap on any sound in the list.
4) If you’ve purchased ringtones from iTunes in the past and they’re still available on the store, you should see the option labeled Download All Purchased Tones at the top of the page.
Tap it and iOS will redownload all
ringtones and alert tones purchased from iTunes using your Apple ID account and make them available right away through Settings → Sounds & Haptics.
And just like that, I got that Jessie J ringtone back that I bought years ago!
Apple cautions that you might not be able to redownload some of your purchased tones, which usually happens if the owner has pulled them from iTunes Store for whatever reason.
You can use these tones to customize your ringtone, text tone, new mail alert sound, calendar alerts and more, as well as set a ringtone or text tone for a specific contact to know who’s messaging or calling you even when an iPhone is in your pocket.