How hard is it to send me a Paid Up LETTER

My name is Lutendo and my id number is ***, my Wonga account was handed over to Anthony Richards and Associates I received an SMS to inform me on the 17 September and on the 19 September I paid the full amount of R4063 which I was owing. I called them the following day and they said they see the payment. They promised to send me the paid up letter the following day I never received it, I called in they said Saturday but I never received it. Today the 25th I called and they said they have sent everything to Wonga and that they are waiting for Wonga to send them paid up letter I then called Wonga but to my surprise the person I spoke to said they can't send Anthony Richards associates the letter until they send them proof of payment. Now I don't know which statement I should take and how difficult is it to issue a paid up letter, I wish they can just send me the paid up letter I have paid everything I didn't even waste their time.