Account payment

I have an Personal Loan at Nedbank. I want to pay extra available money into the account to pay of my debt earlier. I have phoned the call centre a couple of times to get the correct banking details and REFERENCE number that I must used. They once send me the details and it was the incorrect banking details and reference number when I want to do the payment from Standard Bank. I phoned again and send emails a couple of times and never received anything back. Now I must withdraw money and go to the branch to deposit the money. This is not acceptible.