Lie about discount

I have a neotel account which was not paid because i was unemployed. I m currently employed and decided to pay my neotel account which was handed over to nu debt. They offered me a discount of 20% if i pay the full amount. Ive paid the full amount less the discount in November. Uptil now im still getting irritating calls and emails from nudebt but i have settled.. to my suprise now I'm also getting calls from neotel.. the worst part is I'm still listed.. ive called nudebt 4 times and they said they will send me a settlement letter..still waiting..