CANNOT UPDATE, CHANGE, ADD OR VERIFY PAYMENT METHOD

HOW CAN I ACCESS MY FULL ACCOUNT INFO TO VERIFY ALL 16 NUMBERS OF THE ACCOUNT AND TO ADD THE MISSING EXPIRATION DATE ON MY CARD? (I SUPPLY THE 3 DIGIT SECURITY CODE BUT AM TOLD THE CARD WAS DECLINED. MY BANK SAYS NO APPLE REQUEST WAS RECEIVED EXCEPT THE MONTHLY 99-CENT CHARGE WHICH IS PAID AUTOMATICALLY.) APPLE WON'T LET ME ADD OR REMOVE A CARD BECAUSE OF THE ICLOUD SUBSCRIPTION.