You can solve this with the Payment Gateway Based Fees extension. We use that extension for this exact purpose. It allows you to charge a set fee or a percentage-based fee for each of your payment gateways. We have it set only for our credit card gateway with a percentage-based fee.
We and our partners process your personal data (such as browsing data, IP Addresses, cookie information, and other unique identifiers) based on your consent and/or our legitimate interest to optimize our website, marketing activities, and your user experience.
You can solve this with the Payment Gateway Based Fees extension. We use that extension for this exact purpose. It allows you to charge a set fee or a percentage-based fee for each of your payment gateways. We have it set only for our credit card gateway with a percentage-based fee.