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Here's an article providing the steps on how to update your credit card details: https://community.tpg.com.au/t5/Accounts-and-Billing/Video-Updating-your-credit-card-details/m-p/717
That being said, our records show that you were contacted by an Accounts Specialist earlier regarding your request. And from what I can tell, on top of updating the credit card details, you requested to have the account transferred to someone else. An email was already sent to you providing the Change of Ownership form that you need to fill out.
lf you need clarification or have other queries, please leave a comment.