Once a payment enters a Pending/Processing status, neither brightwheel nor you, the provider, are able to cancel the payment.
This is because the processing time is managed between brightwheel's payment processor and the payer’s financial institution.
The best way to resolve this is to wait until the payment has been completed successfully and is marked as Paid. At that point, you can either issue a refund to the parent or apply the overpayment toward their next tuition payment.
Please note that refunds typically take 7–10 business days to be deposited into the payer’s account.