I'm sorry to learn this has inconvenienced you. I checked your Transactions History page, and it looks like you have one active contract on Upwork, that has a weekly salary set, on top of the hours logged by your freelancer. This is why you are being automatically billed. On the same page, you can click on the End Contract button so that you can finally close the contract with the freelancer.
Let me know if you have further questions.