Misleading the customer

I've reached the end of my 24 month contract and decided to carry on just with my package on a month-to-month basis as a result of the current financial situation with inflation catching up to me badly. I got an sms last month telling me that I am nearing my spending limit. I was very surprised as in the 24 months I've never really went over my subscription fees. I logged in to my account and got a shock when I noticed that my bill above my subscription was already on R500!!! I immediately phoned them and they informed me that out of the 1GB of monthly data, only 200MB is part of my package and therefore the 800MB "promotional" data fell away on the date of the 2 year anniversary!? I was never notified of this promotional part and most of all that it will fall away after 2 years!? If I was notified of this I would've either loaded a data bundle or used my 10GB monthly mobile wifi ****le or just worked more sparingly. I lodged a complaint and was informed that seeing as the deal was not done through the call centre and they can't listen to the call, that I should open a new complaint with the store where I opened the contract as soon as the relevant statement is released. This week, when I got the statement over email, I phoned the head office and lodged the new complaint. After some discussions and some waiting period, the agent informed me that it is not mentioned in the contract that the data will fall away and therefore, they will take 50% of the data charges and I should pay the other 50%. I then said that I am not happy as I was not informed of this and it is also not stated in the contract. I was then told that I am fighting for something that I don't even have according to the contract where it was first mentioned that it only mentions the 1GB an nothing about the 800MB that is only promotional. I then asked for a copy of the contract to be mailed to me and the agent said she would do so and confirmed my email address. Since then and after three more requests and an email to the agent, I still haven't got a copy of the contract!? Maybe because this would prove my point? Even if it is written in the contract, I would still be unhappy as I know for a fact that it was never discussed with me and I didn't get any notification that it will fall away. I still have a screen shot of the original adverti*****t from the internet where they are advertising the contract with 1GB data, no mention of 200MB plus 800MB or anything, just 1GB data per month. I would like to be refunded/credited for that and according to what I signed up, I should still be getting 1GB of data per month.