Vodacom contract - Paying close to double

I signed up for a 24 month contract in January 2024, I was asked to pay 50% up front (the contract+phone), which I was happy with. Two weeks later the lady that helped me at the store (the Vodacom Shop in Tygervalley) called me, asking if I had wanted to change my number (I was moving from prepaid to contract), I told her that I did not want a new number. She told me that I needed to come back to the store as she had made a mistake. I was then refunded my 50% deposit.

When I went into the store I made another deposit, the amount was reduced by around R2000. I asked why, and she said that nothing else had changed. I still have the original contract, showing what I should have been paying per month. I have repeatedly tried to sort this out, both at the store and by calling Vodacom. The store tells me I need to speak to Vodacom, and Vodacom tell me I need to go back to the store.

I have spent at least 20 hours of my time trying to sort this out over the course of the last two years, at one point my issue was escalated to a very helpful lady (on the phone) however even though I had her email address, she never responded to any of my correspondence, which contained all of my previous emails to Vodacom, the store etc. I even sent her the copy of my original contract, which I had signed.

I do not recall signing an updated contract the second time I paid (there was a small slip, but that was to acknowledge the deposit) so I do not understand how I was being billed close to double what I was originally quoted. Over the two years this difference amounted to around R6000. Bear in mind I knew the value of the contract, and had worked out exactly how much I should have been paying per month, taking into consideration the reduced deposit.

I am highly ****ed off, and it seems impossible to resolve this.