Overcharged and cheated for faster fibre

<p>Got a call from Telkom: "We can upgrade your fibre speed to 20mps for only R30.00 extra. You'll be charged pro-rata and can cancel anytime." ****************. I've been charged an extra R300.00 (and he DEFINITELY said R30.00 on multuple occasions during the phone call). I have now been charged extra for the whole month of May. I've tried to call them again twice this morning on 10210 and after over 15 minutes of waiting each time I was automatically cut off. How do I cancel this? My fibre also seems even slower now, if that's possible. </p>