The thing is, after I read your thread I actually have tried to open a new figjam file (as I signed up for a Figma professional plan, but not the FigJam professional plan). And I didn’t get charged or will get charged at all.
As long as you haven’t accidentally booked the professional plan, you will use the starter plan, which is free. Do you may have shared your FigJam file with the other person you have mentioned earlier?
Figma won’t automatically book the professional plan, you have to do it manually. So as I wrote before, you must have do so by accident (like clicking around in your team settings or set a checkmark in the booking process of your current Figma professional plan, moving the file to your team, creating a team file or add other editors of your team).
But to deescalate this, you should really contact the support team and most likely they will help you.
Creating new threads might not be the solution to potentially get your money back.
If what happened to you would be the normal and intended behavior, don’t you think the forum would be filled up with angry people?
Edit:
To be fair I just found the following thread, so @christian_banu this might be the thing that happened to you: How to cancel FigJam billing?
As I mentioned earlier, as long as you would have kept the FigJam file in the personal drafts folder, nothing would have happened.
Hey @ksn or any of the other community supporters would you might have a look here?