I'm assuming you have Auto renewal switched on, on your account. They have tried to charge your card for another year of Gold membership, luckily though you redeemed the Gold card, this will delay the renewal untill that subscription is up.
I suggest you turn off Auto renewal via the
account here on xbox.com.
Once complete you have the choice of removing the card all together.
If you have any further issues or questions about the email I suggest you call MS.
WĦo DaRεs W!ηs
Can I change my Gamertag for Free?