Please check if one of the charges is only a reservation. If the subscription is extended automatically, two entries will always be recorded: A reservation of the amount and the actual booking. The reservation of the amount usually takes place two days before the debit. We use it to check whether the account is sufficiently covered and whether the credit card is still valid. If one of these does not apply, the customer will be informed by e-mail. If both are in order, the amount will be debited two days later.

So don't be surprised if you find two entries in your sales. 

If your account has actually been debited twice, please contact support.