To update billing details you'll need to follow these instructions:
1.) Login to MassLandlords.net and click the "My Account" section which is found at the top right of any page.
2.) Scroll down and find the section that says "Subscriptions".
3.) Look to the right of that section - there will be a small black link that says "Update Billing Details" (it is somewhat small and can be easy to miss).