When you signed up there was an offer given to you after the transaction; it asked you if you would like to immediately upgrade your membership. You took that offer and that’s why you were billed the 39.95 for the one month’s upgrade. The site offers this because with the trial you cannot download.
When they sent you the email they meant that the billing cycle is stopped and so you will no longer be charged in the future, But you do have a month acces until October 30th for the month that was paid for.