MTN - making a hash of things!!

On the 9 November 2021 I entered into an new 24 month contract with MTN. This contracted was signed at SABC2398 MTN Store - Cape Gate Shopping Centre L58-Brackenfell. Sales person Kehilwe Gaosekwe who by the way was very helpful. Contract Tariff: 24Mth Mega Talk XS@299. Since then I've been bombarded with incorrect billing. On the 5 January I was sent an SMS saying that if I do not pay R1624.45 I will be disconnected. I then phoned Customer Service and queried this amount. The agent then connected me to her credit manager(?) who said that I will need to go to the store and resolve this there. This I did and this is when Kehilwe assisted me and opened a query Ref: ***. She agreed that the billing was incorrect and that it would now be resolved. She did what ever she had to do on their "system" to resolve the issue. Wrong I had to once again return to the store and fortunately Kehilwe was there and she immediately assisted me. She told me that MTN was trying to bill me for an early upgrade, this is wrong! They were also billing me for a previous data bundle that I had. Wrong! This was not part of my new contract and Kehilwe confirmed this after conferring with the store manager. Another query was then logged on their system *** this was on 28 January 2022. She confirmed that if there were going to be any further costs she would have advised me. On the 1 February I received a SMS from MTN saying that query *** has now been closed. What does that mean? On 3 February 2022 I received a SMS saying that I now need to pay R3209.95 to remain connected??? Then on 4 February 2022 I received another SMS saying that my query *** has been opened?? What's this for? But the very next SMS I received on the same date I'm still asked to pay R3209.95. What's going on ?? Do I now have to go to the store once again? To conclude. I have a contract for R299 x 24mths and a device for which I pay R145 , this is on a month to month contract. If this is not resolved to my satisfaction then I'm migrating. I'm a pensioner and cant afford to drive to the store every second week! I've been using MTN since the very early days but if this is how they treat their customers then I'm out!