The (secret) opt-out URL is: https://www.paypal.com/nothanks

Don't you just love it when businesses trying to push something you don't need and never asked for make you choose "No, thanks" for their pestering to stop. How about simply: "No!" (possibly with an exclamation mark)

In PayPal's case, a firm "no" without a "thanks" just redirects to their Norwegian website: https://www.paypal.com/no

So to opt-out you still have to thank them. Maybe I shouldn't give them any ideas but they could even spin it as "millions of PayPal customers express their gratitude for debit card offer."