Pathetic Customer Service

MTN hand me over to Nudebt management to collect what I owe them. I have contacted Nudebt management and asked them how much I owe them. Nudebt then said that I owe MTN +- R7000.00 and they have received +- R5000.00 payment from me and my outstanding balance was +- R 4000.00. I then asked them what was the R2000.00 for?

They said that it was the money due to them, I then asked to break it down and to date they have failed to that after engaging with many senior staff.