In this particular scenario, it appears that the debt company only have a copy of an invoice. I'm not certain whether or not there is a copy of an agreement anywhere in place.
Opus, who seemed uncannilly relaxed about things on the phone, didn't appear to be pushing for payment but more or less outlined action that I could speak to the college or come back to them if I agree with the amount outstanding, and set up a payment plan.
I just wonder what my rights and responsibilities are in this scenario.