Vodacom is a **** very be careful

Good day Hello Peter. I have aproblem with vodacom. I called in to their call center on the 8th of May 2024 wanting to down grade my data contract because it was finishing too early it was 20gig day and 20gig OWL including 10gig for youtube so i wanted to use wifi that we have at home then the lady as a sales person she then said to me I can't down grade because it's too early and it wont allow me to downgrade of which I understood then she said I can rather upgrade with 70gig day and night data and I will get a free voucher of R500. I said that's fine as long as voucher is for free she said yes it is for free you will only pay your data for R278 . Which was okay. Voucher was then deliver to my home address on the 10th May 2024 I accepted knowing its for free and I signed. So the upgrade for data started on the 1st of June which was fine . So when I get the statement for July 2024 I saw its written headset installation 15 for R25.08 it added to my bill with R278 when I called vodacom the first agent i spoke to she said that means is for the voucher i said but i was told the voucher is for free then they said they are investigating. I call again the other day then I was told it's for headset i told the agent i never received headset then he said we can send them to you i said i dont want them. Then he put me through to reward i spoke to another agent who promised to get back to me after they finished investigating. Since then I haven't received any call and I even received another invoice with the headset installation 15 included I'm expected to pay for something i didnt received in the meantime while they are investigating. Hello Peter please assist.