Vodacom

I keep on getting messages that one of my cellphone***) contracts with Vodacom is ending. I must upgrade today or if I don't then the contract will continue on a month-month basis but the problem is Vodacom don't provide its customers with details on how to cancel their contract should they no longer need it. I searched on the internet as to how I can go about cancelling this contract. the only number that is there is 082 111. I dialed that number and it is not working at all. I also dialed 135 and was kept on hold for hours with no help.