>> I don't think any responsible bank would let you withdraw using just an account number.
That is literally how checking works in the united states. You can withdraw money from a bank account if you have a routing number and bank account number and "permission." The permission could be a signed check, it could be an auto-pay ACH you set up by handing a paper form to someone, it could be a web-form you signed without looking over the fine-print.
Most extractive companies (e.g., gyms, verizon) have so many fine print and so many lawyers that they can literally take anything from you without recourse. You'd spend tens of thousands in lawyer fees without getting the money back. You could go to the attorney general's office for your state. Good luck with that, unless its a common issue, you just have to eat the cost as part of being American.
Or it could be nothing. In this case, its still on you to figure it out and get the money back in time.