Unauthorised change of contract

Received a call from a Vodacom salesmen, Mohammed Kareem, that my business contracts are no longer allowed to be on a SMART L contract due to the amount of usage on the contracts. He said I needed to change to a higher package. I enquired on the cost involved & was informed that this would not cost me anything but rather save me about a R1000.00 per month. Imagine my surprise when I was viewing my usage for the month & both contracts had a charge of R1999 for RED subscription. Sent Mohammed an e-mail advising that this needs to be removed as I did not agree to any increased cost on my contracts. I am in the USA & have phoned cancellations 3 times with 1 telling me i must have agreed and put the phone down on me. 2(Elsie) refused to provide me with a reference no. & 3 (Thembehle) cut me off as well. I need to have this matter resolved before the next debit order is processed as I am very unlikely to get the R4000 back from Vodacom once it has been debited to my account. Does this mean that anyone at Vodacom can process charges to any individuals contract without any authorisation. This amounts to ***** which is a ******** matter.