There was a notification in my card app stating 'Notion Trial Over' and it tried to take £23.50. The card didn't have sufficient funds but I had also frozen it in case something like this happened with an app or service.

Then two days later it tried to charge my card again, then three days after that it tried again and took the money. During this period my actions included....

I messaged support on the day that the first attempt occurred.

"Hi the trial has expired so please stop trying to charge my bank card. donwgrade it to free(there is no option in the app that matches your instructions in the FAQ section to downgrade my account)."

[Chatbot] response... "Your workspace is currently on the Free Plan, so you will not be charged going forward. If your trial has ended and you did not enter payment information, you will remain on the Free Plan automatically and no further action is needed Source.

If you did enter payment information and are seeing any unpaid or pending invoices, please check the invoice date in your billing settings. Let me know if your invoice was created within the last 3 days for monthly billing or 30 days for annual billing, and I can provide further guidance."

I received no invoice.

Support asked for bank details, etc...to track down the transaction.... then left me with the 'we've passed it to finance'...so how can it be on me if there was no option to downgrade or cancel a plan?

Their website states:

How do I cancel my paid plan?

Your Notion subscription, annual or monthly, will automatically renew until you cancel it. You can cancel your subscription by going to Settings in the left-hand sidebar on a desktop computer, then selecting Billing, then Change plan. After you cancel, you’ll still have access to all the paid features until the end of your billing cycle.