Impossible to change credit card

Hello, good day and thanks for your question. You may check and try doing this on a different browser or try using InPrivate or Incognito browsing depending on the ones that you are using and the last option is to try and use PayPal and connect your card from there. In the event that you will still encounter an issue, you can reach out to the support team at https://support.microsoft.com/en-us/contactus/ and then click on Microsoft 365 and then click Get Home Support and then type in Billing question and click the blue button that says Sign in to contact Support and login and proceed from there or you can also request a call back by going to https://go.microsoft.com/fwlink/?linkid=2168171 and it is best to do this on weekdays instead of the weekends.