send me my paid up letter

I have paid up my Truworths account with NRB ltd attorneys on the 30/03/16. When I phoned them on friday 8/04/16 they promised to give me my paid up letter on that day but they did not send it. When I phoned them again on monday 11/04/16 they told me they are also waiting for my letter and they do not know when will I get it... Now what am I suppose to do now, I cannot wait for something I do not know when is it going to happen..How hard can it be to just send me my paid up letter coz it has been confirmed that I have settled my account.