Log into My T-Mobile.com and click on the "Profile" tab at the top right of the window.  Under "Billing and Payments" you can change and delete card info.

Hey, @yiwen1031​! Just wanted to check in and make sure that you were able to follow the steps above to edit your card info! Please let us know if you still need help!

- Marissa

I could only see adding a new card details. Don't see options to remove. Please can anyone share the steps to remove existing card details

Are you enrolled in autopay? If so try cancelling.