Hello there, synapse_med.
I'm here to route you to the correct support that can help you update the billing information of your Biull.com account.
You can go to this page: Bill.com. Then, go to the Contact section.
In case you also want to update the billing information of your QuickBooks Online account, you can check this article: Update the payment information for your subscription.
I'm just around if there's anything that I can help. Stay safe!