The key here is that the ADA repealed (or better put, supplanted) Rule 240 in 1984. It's now air carrier slang and has no legal meaning. Many younger agents will never hear the words spoken.

Always best to explain what you want rather than citing rules which may not even exist and if they exist, apply.

Next step is to figure out what you are entitled to vs. what a carrier could do to help you out in a bind. To that end, check the endorsements.

Might an agent take pity and rebook you OA (even non-*A)? Perhaps, but a hard sell and not something on which you should count happening.