Vodacom does not give you what they sell you

On 5 July 2018 I app**** for a Vodacom contract. The deal I app**** for a 10GB data price plan topup @ R249 per month. A while after Vodacom contacted me and told me the router that comes with the deal I app**** for was out of stock, but they can give the same deal, just with another router. I accepted that deal. End of September I noticed an amount of over R4000 deducted from my bank account by Vodacom. After enquiring about this demand, I was informed that the contract I was signed up on was an open line and not a topup plan (as I was led to believe), and that I had used out of bundle data amounting to that amount. I disputed this, saying it was not the product that I bought from them and that I shouldn't be held accountable for the outstanding amount, as the contract I app**** for, was supposed to stop once the data ran out. Vodacom then admitted they were in the wrong and I didn't have to pay the outstanding amount of over R4000. They also informed me that there is now another amount outstanding for out of bundle rates used of over R1700. And even though they admit it was their mistake, I still have to pay the outstanding amount. I logged another service request to dispute this amount - because the contract I app**** for still had to stop once I used the data bundle up. They logged the service request and told be they would call be back the following week - I never received any feedback on that service request and I am now receiving threatening messages from Vodacom saying I have to pay the money within a certain time. No one seems to care that they did not give the product that I was under the impression I bought - according to me that is *****. I am now stuck in a contract that I DID NOT apply for, and owe money for data that I was not suppose to have used if they had given me the contract that I app**** for in the first place! No one at Vodacom seems to care all they want is their ********** money. I have been a Vodacom customer for many years and never have I received such awful service from them. Vodacom admitted that they were wrong, but I am still being held accountable for their mistakes - how is that fair?