HOW DO I CANCEL A CHARGE????

HELLO I AM VERY NEW TO ITUNES AND STUFF. I WAS VERY INTERESTED IN NETFLIX. I ORDERED A ONE MONTH TRIAL AND ONLY USED IT ONCE. I WAS SURPRISED WHEN A $32.80 CHARGE WAS MADE. I WAS SAVING THAT MONEY FOR MEDICINE. NOW I HAVE ONLY $6 IN THAT ACCOUNT.

IS THE CHARGE FOR NETFLIX?? I WISH SOMEONE WOULD HAVE TOLD ME THAT THE CHARGE WAS COMING SOON.

WOULD YOU PLEASE REFUND MY $32.80??

THANK YOU