Involuntary Update of Credit Card Details?

Hi there.

I received an email from Norton, indicating that my CC had expired. I've not updated to my new card, by choice.
Today, I log into my Norton Account, to Cancel 'Auto-Renewal'; I find my new card details logged in 'Billing-Information'.
So, how have Norton obtained my new details ? Is the exchange of secure details common place ?

What happens if I delete the card details. Does Norton continue to function. Alternatively, am I expunged from the list of users ?

Any info would be appreciated !