Total incompetence of Vodacom Billing / Cancellations

I ported my number to Cell C, paid the early cancellation fee as per Vodacom quote end Feb 2017. I was not told I had to separately go and cancel the contract. Did this after I received an invoice after the port had been done. Could not do this per telephone so went to Vodacom Dainfern Square. They called the cancellation department for me - I spoke with cancellations who assured me the contract was cancelled. I continued to receive invoices. In December 2017 at my wits end I went to Vodaworld in Midrand (visiting Joburg from Cape Town) at my own cost (taxi fare of +R200) and spent FOUR HOURS going through the same process as I'd been through several times previously. Again, I was assured the contract was now cancelled. No monies owing. I have just received an invoice again. I called Vodacom Cancellations. They assured me the contract is cancelled. They transferred me to Accounts, who told me my contract expires in March 2019!!!!! What this shows me is that they started a brand new contract, unknown to me, as of when I cancelled the original contract but against their "ghost" number (an 079 number) that they allocate when a number is ported. I have now spoken to five different people at Vodacom today. One of the people in Accounts told me that this "ghost"number is a Twin Sim number that wasn't cancelled at the time. However, the only time I ever had a Twin Sim (which was cancelled long ago) 079 numbers didn't exist yet. I have now been on the phone for several hours and have as yet not been able to resolve this issue. I have never come across such an *********** company as Vodacom. How is this possible???