Done paying debt now suffering

Paid my final debt on 23 October. Got informed 2 November that i was double refunded and Debtor was doubled paid(their error). I paid back their refund on 3 November. Till today no paid up letter, no clearance certificate. I stuck to my agreement with them even finished debt review early. But now my life is stuck, they are not responding to my emails, when i call them their explanation does not add up. I also called the debtor, debtor acknowledged overpayments and says the refund within 24 to 48hours. Im done paying all my debt, i dont understand why now im made to suffer like this. I looking at the legal route as this cannot be right.