I would probably call anyway - just to make sure it was processed correctly.

I cancel and refund tickets all the time for all sorts of reasons (nearly all the tickets I buy are refundable for this very reason). Sometimes I do this within the 24 hr window but usually not (actually, I usually do it after the trip dates have past and I am sitting down to do my expense reports).

I've noticed that the process varies between the easy (seemingly automated) process and the more details (perhaps manual) process. Both are usually posted back to my credit card within a week or so. My guess is that, under certain circumstances, the system cannot confirm that a ticket is refundable and flags it for manual review (hence the more detailed form). I've noticed that if I'm upgraded, for instance, the longer form is always what comes up.

PS -- I'm talking here about the post-24hr period. IME canceling within the 24hrs always is the same process.