Nedbank fails spectacularly again

More than 10 years ago I held 4 Nedbank accounts which due to terrible service I then closed. Now, a decade later they have started calling me from NRB Solutions- a debt collection company for outstanding bank fees. 1. How can you hold me liable for an account you did not close when instructed by me to do so? 2. How can you contact me a decade later for this? I don't even know the account details it's so long ago! 3. It was apparently handed over in May and since then I get constant calls from this debt collector which feels like harassment as I told them all this information and they just keep calling. Pathetic service from Nedbank once again!