Vodacom messes my debit orders every month

Two months ago my contract was changed without my consent and I was billed R504 instead of the usual R170. I called in to complain and this was rectified. I just realised now that yesterday (01Aug) a debit order of R205.99 went through. I don't understand how we moved from R170 to R205. Can someone please clarify this, and while at it, please refund me and cancel the contract. I don't even use the phone. I can go for days without making calls, clearly I don't need it.