Poor service

Vodacom claims I owe them money from expired contract, however, they are unable to give me a statement as to how the missed payment in question has come about. Moreover, they are unable to provide contract they claimed have signed that talks to the clause they are using to make me pay. Today they (vodacom) have blacklisted me for what, nonsense - just because they can. This is total nonsense and these big companies think they are so powerful, they can get away with ill-treating its clients. People must think twice before taking any contract with Vodacom - the next thing you'll be blacklisted like me for no reason. It has been over a year I have been requesting a statement and copy of contract, and they (Vodacom) fails to provide - how/on what basis did they blacklist me? Is it through ******* means?