Horrible service from supersonic.

I had a pre paid data subscription with supersonic, it inly worked wnen i bought a voicher at shoprite snd pre loaded it in order to get data. I stopped using it years back now i have rude debt collectors haunting me every day saying i owe supersonic money. I asked them to send me the bill detailing how i owe them but they refused, they say i must just pay or they will black list me.when i contact them via the WhatsApp i used to load on, no one vall me back. Guys stay away from supersonic.