If you buy product that asks dollar currency then it will use balance. (if your card is in Euros and you buy product that is in euros then it will charge card.)
During the checkout process, you should have the option to choose your funding source however, there are some merchants or vendors that will only accept a credit card and in many cases, if you are purchasing a subscription or setting up a recurring payment with a merchant or seller, a credit card is usually required. Since this is a public community whereas no one here can look at user account transactions, it's not possible to provide a good answer other than a general statement.
Click on the profile tab (icon next to log out) > Click on payments third option along on the thick blue band top of page > second down click on update next to your prefered way to pay and put a dot in one of the options listed.
Advice is voluntary. Kudos / Solution appreciated.
