Impossible to cancel credit card

It's impossible to cancel a card with Discovery. half a month later, 10 phone calls later and i am still struggling. proof that the given email addresses do not work (emails bounce back). *** (bounces back) *** (not monitored) service agents unable to call out and a company policy that they cannot share personal email address makes it a total nightmare. this is borderline ***** being committed in not being able to cancel a service?