Handed over

Had a cellphone contract with Mtn, which ended February 2015, I phoned customer care in January about 5 calls to inform them I wont be upgrading due to their bad service n network problems. In March they Debited my account for no reason I'm fami**** with and I reversed the transaction. To my surprise today 10/06/15 my bank told me I have been handed over to Credit bureau for what and how much I don't know, I never received a warning call,mail or SMS to inform me of such actions. I tried to call the customer care and the rude consultant hanged up the call on me. Like what the ****, are they bitter coz I didn't continue with their services or what. I hate the ****en Mtn Brand useless network in SA and on a campaign with my legal team to root its filthy Mafia tendencies.