Disappointed customer

After cancelling contract , I got messages that I owe R2600 which I paid due to understanding that I was still receiving data and asked them to cancel. And person assistanting assired it’s closed , 6months down the line I got text that my account has been handed over to MBD for R615 that I owe and I paid it two months ago , was promised to receive settlement letter from MBD and Vodacom but nothing till today , when I call them they don’t answer this days they kept saying I will get it in 24 hours but I’m still blacklisted and no letter they don’t even respond to my calls