Which phrase would you use to inform someone of your intent to cancel a previous instruction?

Using the phrase "Cancel last message" is the most effective way to communicate your intent to revoke a previous instruction. This phrase is clear and direct, ensuring that the receiver understands that they should disregard the last directive given. In critical situations where communication accuracy is paramount, clarity helps prevent misunderstandings that could lead to mistakes or unsafe scenarios.

The other phrases do not serve the same purpose. "Return to station" suggests a change in location rather than addressing a cancellation. "Standby" implies that the recipient should pause and wait for further instructions, which does not explicitly indicate that something previously communicated is to be disregarded. "Receiving well," on the other hand, is used to acknowledge that communication has been understood, but does not convey any intent related to canceling an instruction. Overall, "Cancel last message" is the most suitable choice for effectively notifying someone to disregard the previously given instruction.