In my experience, you need to call in and go through the hassle of requesting them to give back your credits. The issue with Eplus and WorldMark is that Interval does things correctly, (and gives you the retraded resort), but WM does not. WM sees the retrade as a new exchange, so that means they take more credits AND a housekeeping token. While you're on the phone with them, ask them to review the exchanges you have. WM will (likely) see you have two exchanges checking in on the same day, but at different resorts. You need to convince WM to hand you over to a Supervisor who understands how Eplus works, have that person review your account, cancel the older exchange, and then request from the IT department that the initial credits be returned to your account. The last time I did that it took about six months before WM finally made things right. It's a major PITA. The lesson I learned, and that Tuggers confirmed, is to not use Eplus with WorldMark. I learned my lesson.
Good luck!
Dave