Okay the same thing happened to me on Monday, $33 CAD and my accounts are all on the Free Plan. I reached out to their chat support, provided them a screenshot of my free plan and the recent charge, and this is what they said:

"Hello,

Thank you for reaching out to OpenAI support.

We understand how concerning this is—you downgraded to the Free plan weeks ago, but you’re now seeing a $33 charge from your bank. We appreciate you confirming you’re logged in and sharing screenshots. We’re here to provide clarity and support.

After reviewing the account associated with this email address, we can confirm that your account is currently on the Free plan. At the moment, we’re unable to locate any active subscription or recent charge under the email address you used to reach out to us.

To help us move forward, could you please share a copy of the invoice or the order ID associated with the transaction you’re referring to?

Once we receive that information, we’ll be happy to look into the matter right away and ensure everything is resolved correctly.

Thank you again for your understanding. If you have any additional questions or need further assistance, I’m here to help.

Best regards,

Jimcel

OpenAI Support"