iTunes Account

[BigBrotherfan4ever]

I've got a iTunes account I've not used for a while but decided to download a book today it asked me to update my bank details, but things is I've got got vouchers stored in the account but they took money out my bank account & not off the vouchers, does anyone know how I can sort this, I would rather I use the vouchers at the moment.

Thanks:xyxwave: