I don't think there's a great solution in these documents but at last you'll learn a bit more about "other".
How to check the storage on your iPhone, iPad, and iPod touch - Apple Support - http://support.apple.com/HT201656 - "About cached files in Other ... When you stream music or video, that content is stored as cached files on your device so you can quickly access it again. Your device automatically removes cached files and temporary files when your device needs more space." "You don't need to delete them yourself." (Which I interpret to mean you cannot delete them directly yourself.)
How to Clear "Other" in your iPhone's Storage - Use Backup
https://discussions.apple.com/docs/DOC-250002774
- A somewhat drastic but oft mentioned solution achieved by making a backup of your device which will not include "other", erasing the device, then restoring the device from your slimmed backup.
Clear the history and cookies from Safari on your iPhone, iPad, or iPod touch
https://support.apple.com/HT201265
What is "Other" and What Can I Do About It? - https://discussions.apple.com/docs/DOC-5142
Check the cellular data usage on your iPhone and iPad - https://support.apple.com/HT201299
- "To see the cellular data usage for individual System Services, go to Settings > Cellular or Settings > Mobile Data. Then scroll to the bottom of the screen and tap System Services. Cellular data can't be turned on or off for individual System Services."