Was handed over to the credit bereuw

I've been paying faithfully paying cellphone contract for 24 months and I called to cancil the contract on the expiry date and was told it has been canceled and after 5 months I reaceved an email stating that I've been handed over to the credit bereue and need to pay R9000 within 10 days.<br> I do not know for what and when I call mtn they keep telling me that legal team will contact me but they never call. I was never notified of any areas in my account no letter no phone call from mtn. Who does this to their customer. I don't even know what to do now.I regret doing business with mtn.