Vodacom aggressive selling

I received a call from the Vodacom marketing people during the second half of 2023 and as they normally do, they talk too much too fast for older folks like me to follow. I said that they must put everything they said on an e-mail and send it to me and I will respond. In September 2023 I was informed that my new device was being sent to me. I immediately said I didn't want any new device but it was delivered. I contacted them to retrieve the device which they promptly did. Having done that I assumed that the offer made telephonically was thereby cancelled, even if they activated the upgrade without ever sending the details for me to evaluate. Recently I visited a Vodacom for me outlet to review my package because, being retired I need far less data and airtime as when I was still employed. I was told that because I upgraded during 2023 they could not do a downward migration for me to reduce cost without a penalty. I reluctantly accepted and subsequently I received an invoice exceeding the amount I expected to pay. The lady at customer care helped me to analyze the account and it transpired that all kinds of extras had been added. She said they cannot change anything listed without a further migration fee, despite the fact that it was never discussed with me. So I'm now convinced that they are out to extract as much from me as they can with total disregard for their own errors in communication with me. The problem is that the staff at the outlet I visited told me that they are not authorized to change agreements.