If your refund is delayed at the IRS for an unusually long time, or if the IRS reduces your refund such that it is no longer enough to cover the fees, TurboTax would then send you emails asking for payment. If not paid, they ultimately notify you that they are about to debit your bank account, and then do so if not paid.
You should be getting emails from TurboTax regarding your TurboTax fees. You can also contact TurboTax support regarding your TurboTax fees.
https://support.turbotax.intuit.com/contact/
