In most cases reported to Soundtrap, authorizations are often mistaken for extra charges. Authorizations are the result of normal bank processing and are automatically resolved by your bank.
A little background: when a payment is processed, a bank authorization is posted to a bank account statement while the charge is pending. An authorization is required for all credit card transactions as a passive check to ensure the amount of money being charged is actually in your account before the funds are transferred. These authorizations can appear on your billing statement next to the actual charge and appear as if you are being charged in duplicate.
Most banks will mark authorizations with a visual cue, such as the word "pending", to identify it as an authorization. Typically, these authorizations are automatically removed without affecting your bank account balance as soon as the actual charge is applied. Some banks take up to two days to remove authorizations but you can verify this with your bank by calling the number on the back of your credit card.
If a bank authorization can be ruled out, please contact us at support [at] soundtrap.com and we'll be happy to investigate the issue from our side.