Billed incorrectly and still waiting for my refund

I contacted Vodacom in October to cancel a contract that reached it's end date. What I thought was good customer service at the time turned out in a nightmare. I was advised to downgrade the plan to a WhatsApp bundle for R25.99 per month which I was completely happy with. Upon the receipt of my Vodacom statement I noticed I was billed for a Uncapped Home Internet 5G Best Effort-Top Up at a rate of R1298.99 - I did not agree to this service. I was promised a refund due to the error but have not received it and every time I follow up I get told it will be escalated. I need the funds you have debited from my account (without my approval) refunded ASAP or I will escalate it to the regulator.