Since we are a Canadian company, sometimes customers in the US get charged an international transaction fee by their credit card company, even though we charge in USD.
These companies put this charge in the same line item as the charge from us, so in most cases, the customer won't notice the charge by their credit card company. They should, however, put a separate line item stating what the additional charge is.
If you contact your credit card company and complain that they buried the charge in the transaction, hoping you would not notice, and that the transaction is processed in USD from a USD processor, so there should be no international fees even if the end receiver of the money is in Canada, it is most likely that you will get the fee refunded and never be charged again.