I got an email stating there is something wrong with my payment information and icloud can't charge me the .99 cents for my additional storage I get each month. Tried the instructions but can't find where to check my payment info

I got an email stating there is something wrong with my payment info and icloud can't charge me the .99 monthly fee for my additional storage I purchase monthly. Tried the instructions and couldn't find it. I went into the App Store (ITunes) and it had an old credit card and address. I updated info but it then said it couldn't accept my payment method???