Marking assignments to allow the student to finish the course

My son was registered to complete a certificate in Supply Chain Management and part of this process was to submit assignments. Assignments can only be submitted once the previous one has been completed. Since last year he has been waiting for assignments to be marked in order to submit the new one however it never gets done. I have logged complaints but am only told that my complaint has been directed to another department but they don't respond. It doesn't stop them from debiting my account though. He cannot finish this course and look for a suitable job because off all this issues. I need an urgent resolution to this issue.