I know United allows free cancellation to award tickets (and other tickets) within 24 hours. I don'tn have status on United, so some changes to tickets (change of carriers, change of origin/destination) normally cost me money.

If I purchase an award ticket, can I call in and simply make any changes for free within 24 hours (subject to repricing of miles, higher taxes, etc.) ? Or will they require me to cancel the booking, hope the award inventory reappears, and start over?