Vodacom is ****ming customers

From March 2021 I have been a loyal customer of Vodacom. I signed up for a month to month 10Mbps Bitstream Uncapped internet for R604pm. Even though I knew this was expensive compared to other ISP's. I still decided to go with them. Everything seemed fine all their time and at some point I got upgraded to 25Mbps Bitstream but the installment remained the same. 3years later I see a debit order of R829 from vodacom and this amount was debited end of April 2024. Upon seing this I immediately called vodacom to understand what was going on. They told me that all their customers were automatically upgraded to 75Mbts Bitstream in April and I didn't called them to correct this,so hence there was a debit order of R829. Obviously I was unhappy about this and requested to cancel my contract. They begged me not to cancel and told me that i can get downgrade to 25Mbits Bitstream at R539pm. I decided that I will stay with them and not cancel anymore. Please note that all this happens on 30April and I was told that from 1 May 2024 I will be on 25Mbts Bitstream for R539. Today being 31 May 2024 I see another debit order of R829. I called and requested answers and their billing department says I get billed in advance hence the R829 and that from June my account will go back to the R539 as per the new contract. Can someone please explain what kind of **** is vodacom is running. This is totally unacceptable and the customer service agents are not clued up about the difference between billing in advance or in arrears. Now I requested a cancelation of my contact and I'm told I need to give a calendar month notice ( which is fine) but I will still be liable to pay the last invoice at the end of June. So if there's one last invoice to be paid end of June, then which month is that invoice for? This is ****ming on another level. And as loyal customer for more than 3years I'm so disappointed. I will definitely be spreading the word on social media and I will make sure no one ever takes up this fibre contract with Vodacom. Because it's expensive anyway