I managed to cancel a (non-edu) Adobe subscription a few years ago, despite being a few days past the cut-off date for cancellation.

What worked for me was to phone them and insist on cancelling. The person I spoke to insisted right back that it wasn't possible. When I persisted they offered me an extended term for the same price. Then a discount, and then a better discount. After that they agreed to cancel.

My impression was that they had a customer retention flowchart to work through, and it was just a matter of getting to the right terminal node.