So, update.
My partner sent EduStaff a screenshot of the pay code and assignment EduStaff switched without informing my partner.
The screenshot was of a past assignment from December that was the same classroom, same school, and had the $200 pay code, but was switched to a lower pay code in June AFTER my partner had already accepted the assignment, which was deceptive on EduStaff's part, because my partner had they known, would've cancelled that assignment and chose the one with the $200 pay code.
This is EduStaff's 'defense' 🙃
They said my partner was "overpaid"
Apparently, temp agencies can go back in and switch things up to support their gaslighting of substitute teachers who keep receipts