Paid up letter & Debit order

Ive made arrangement with them to paymy outstanding Edgars account in 2 debit orders to settle my account. After the last debit order was paid end Oct I phoned them to send me paid up letter by mail twice. I am still waiting. I had to reverse a debit order went through my bank account today although my account supposed to be settled. Phoned them once again today to send me a paid up letter. They promised again. How long must I wait and paid cists to reverse wrongfully debit orders.