Frustration at closing credit card

I have been trying for over a month to cancel my credit card. The first e-mail I sent I got a response after 2 weeks telling me I had to complete a form which I duly did and paid the outstanding amount on the card. I sent this back exactly one month ago yesterday and have had no response since. I have sent follow up e-mails, I have even laid a formal complaint. This too has gone unanswered. Absolutely disgusted at the decline in service from Discovery. Never thought I'd see the day.