There should only be pending charges, not actual charges. The pending charges should disappear after a few days. If they do not, contact your scheduler.
If you are doing a lot of these shops, those pending charges can add up quickly and affect the available credit on your card(s).
Yes, some of the hotel employees are clueless. They don't read the letter carefully and they don't want to do anything out of their comfort zone. Many won't do the cancellation right away. Some, however, do it right away and may even give you a printout that proves they canceled your stay.
Good luck.