If you need to change the bound bank card number on the Postal Savings Bank client, the operation is relatively simple. The following are detailed steps:

First, open the mobile banking client of Postal Savings Bank of China, find and enter the credit card management interface. Since the additional option may not be displayed initially, you need to click on the main menu in the upper right corner, enter the settings area, find and click on the "Account Management" option.

On the account management page, you will see an "Account Add" option, click to enter. In the next interface, enter the number of the new bank card you want to add, making sure the information is accurate.

After completing the input of the card number, click "Next" and follow the prompts to fill in the necessary personal information, such as name, ID number, etc. After confirming that it is correct, click "Confirm" to bind. The system will prompt you that the binding is successful. At this time, please check the main menu again to confirm that the new bank card has been added to credit card management.

Finally, return to the credit card interface and you will see the new bank card option. Click "Credit Card Account Inquiry" to view and manage the billing information of your newly bound bank card. In this way, you have successfully changed the bank card number on the Postal Savings Bank client.