Can I cancel a claimed substitute request?
When a substitute request is claimed, a new one-time substitute commitment is created for the adorer who claimed it, and the requesting adorer is notified that a substitute was found.
Thus, you cannot cancel this substitute request.
If the adorer who claimed the substitute request did so in error, or now needs a substitute of their own, they can simply request a substitute! Or, as an administrator or captain, you can do this on their behalf.