It's important to note that if you signed up as a business or sole trader you will have been given two profiles, a personal one under your name and a business one. When you log in you will automatically be taken to your personal profile, to switch profiles go to account and scroll down to relationships to select your business profile. When adding a payment method you must ensure that you've entered the correct account first; for security reasons you can only add each individual payment method to either your business or personal profile. You must then check when you go to pay that the 'account selected' is the same one as you loaded the card details into.