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The auto debit would still continue to work, right ?

My SI for X premium was not processed so I had to update the payment details through another card. 15th July is the date for complete migration so nothing will work after that unless updated.

So I had a standing instruction for the Credit card to pay the total by due date, are you saying, we need to recreate that ?

If you are using citi bank account then yes you may need to update as far as I am aware. I have already removed all SI from my citi account to avoid any issue but for more clarity you can check with customer care team once.