Unlink a subtitle from a video on your account. Don't forget to specify DELETE as the request method.
https://streamio.com/api/v1/videos/video_id/subtitles/subtitle_id.format
DELETE
200
This example unlinks a subtitle with id 4cd2be8454129008dc00000e from a video with id 4c48388bbf4b9802c5000007.
curl -u username:password \
-X DELETE \
https://streamio.com/api/v1/videos/4c48388bbf4b9802c5000007/subtitles/4cd2be8454129008dc00000e.json