Unhappy Client😡😡😡

I had a loan with Nedbank which was handed over to NRB.They contacted me and I made arrangements to pay which I did.I was recently offered a settlement amount and I paid it in November but they have not issued me with the paid-up letter.I have been following up with them and they keep on telling me that they are waiting for Nedbank to issue the letter.Why didnt they tell me to settle Nedbank directly if they knew that they not going to do their job.The money is in their account but I must be the one following up on them,this is not fair.They must do their job and issue me with my letter