Early cancellation of contract

I requested an early cancellation invoice from Vodacom and they sent it to me. On the invoice it says “early cancellation discount”. After paying the exact quoted amount and followed steps for early cancellation including doing a follow up; they delayed processing the cancellation which according to them meant I still owe for the months while they hadn’t processed the cancellation. On top of that, they said I only paid for the handset and hence the contract itself will continue until the last month. This obviously defeats the aim of the early cancellation and it means they didn’t apply the discount. I’ve been attempting to liaise with them but I am not getting any help. This is such a horrible experience and bad customer service.