I understand that encountering challenges with your QuickBooks account and feeling let down by the unavailability of weekend support can lead to feelings of disappointment and frustration, H-ma. I wanna make sure you'll get the help you need.

You can update your payment method by loggin in to your Customer Account Management Portal (CAMPS) as the Primary Contact, as advised by Fiat Lux - ASIA. This portal allows you to manage your QuickBooks product and account information.

Here's how you could do it. 

1. Open a web browser and go to the QuickBooks CAMPS login page.
2. Enter your Intuit account credentials, which are the same as the ones you use to access your QuickBooks Desktop software.
3. Click on the "Sign In" or "Log In" button to proceed.
4. If prompted, verify your identity using the provided authentication method (e.g., email verification, security questions).
5. Once logged in, you will have the ability to make changes to your payment details and perform other account-related tasks.

Still, I highly recommend contacting QuickBooks Desktop support for further assistance regarding changing information in your QuickBooks account. Our Support Team can pull up your account in a secure environment and then run a set of examinations.

Within your QuickBooks Company file, select QuickBooks Desktop Help from the Help menu. You can also press F1 on your keyboard to bring up the same Help panel. 

Additionally, here's an article for more details: Change, manage or update your Intuit account with CAMPs.