On the Yahoo! Store Manager, you should see an "Store Account Info" link that you can click to go to the page containing the technical contact and billing contact information for your store.

You can also select whether you would like to receive a copy of the Yahoo! Merchant Solutions Newsletter by checking off the appropriate box in the Email Me section of the contact information. This is also the page where you could change billing information, such as the credit card being used to pay for the store.

You should be able to update this information as necessary. After making any changes to this page, you will need to click on the "Change" button to save the changes.