I have a Wordpress-based social network site that has a paid access section for premium members. It uses the Verotel Flexpay API. All has been well with processing cards until a member hit a snag with his bank's security. Long story short, he needed to switch cards. When I canceled his paid account so that he could re-apply, he encountered a "website configuration error." Apparently, there is an issue with cancelling from the vendor side and the database being updated. I believe that the postback script may not be handling the credit postback correctly. I need someone to review the script and debug.
Freelancer needs to be experienced with Wordpress and working with API scripts. Full stack level of competency desired. No beginners, please.