Retroactively correcting GL Department Information?

Our issue is that new items were created with reversed credit and debit DeptID's in August and only recently discovered to have been wrong, in that time 1300+ transactions have taken place with this incorrect GL information. They were also all posted individually, no group post, and we have not been able to find any functionality to reverse all payments associated with these item types to then reapply them, nor any method that wouldn't reflect on the students account. Is there a way to correct this information retroactively in Enroll & Pay/Campus Solutions? We've ran a process in a test