Payment letter, account not cleared

Good day

I am really not happy with the service, I paid up my account in full with wonga in March. One of the representatives from the law firm called to confirm payment and stated I would receive my payment in 7-14 days which didn't happen. I personally called wonga in April to confirm the payment, they confirmed the account has been paid off, they said my account will be cleared in 21-30days of April,end of April I checked my credit the account was cleared, it showed I never made payment in March. I called again to request my letter, I still haven't received it, sent an email last week, I haven't been assisted.

I'm really disappointed with the service