Refuse to assist with errors on their site

Payfast reject a payment with a "Incorrect card number" error after payment was approved on the banking app so clearly the number was correct. They refuse to even investigate the issue referring you to the merchant. The only feedback the merchant got was that it is a bank related-expense and I need to speak to the bank. No reference number or anything that might assist me in trying to resolve their issue with the bank at all. From now on I will avoid any site that uses PayFast as their payment gateway