Sorry, I'm not doing hypotheticals this morning.
Let's get really, really simple though - if you call someone and they have an answering machine and you leave a message ... you have consented to them recording you even if you change your mind afterwards. If you change your mind while you're actually talking to a person, then you hang up. What you say before you end the call can still be used against you, but truthfully the issue of revoking your consent (and indeed, when you may do so) is actually a lot more complex than you might think.

