Sim only data contract that does not support 4G which I was promised of.

I took a Sim only data contract with Vodacom in last November, not because there were no alternatives but because Vodacom promised 4G internet speeds. But the Sim card does not support 4G, I took it to Vodacom Shop, they told me they could not fix it so they suggested that I buy another Simcard and do a sim swap. I was even asked by 1 of the consultants at the shop "why do I need 4G". That gave me an impression that my Sim card is blocked intentionally so that Vodacom can forfeit my data after I could not use it due to poor internet speeds. I did a Sim swap but still the Sim Card does not support 4G I have been contacting their Call Centre and sending emails they do not seem to be interested in sorting this out. I already paid for 3 Months for very poor 2G and sometimes 3G internet speeds. I cannot keep on paying if they do not fix this.