Your debit/credit card will only be charged once.
If you just placed your order and you received an error at first, the second charge you are seeing is an authorization. This is a common bank practice handling credit card transactions to ensure sufficient funds and account authenticity. This authorization will clear and is 'pending' (depending on your bank, usually within 48 – 72 hours.) If you need help speeding up the process, you can contact the issuing bank of your credit card.