Incorrect tariff billing

On the 2nd Feb 2021 I upgraded my contract phone from a R299 tariff phone to a R449 tariff phone. In April 2021 I noticed that I was debited way more than I signed up for. So, I then checked my March debit order only to find that I was billed R2601.42 In March and R1988.99 in April. I then visited the store where the account was opened which is MTN Eastgate on the 3rd May and the consultant there informed me that the system indicates that I am on a R1700 tariff contract, she then logged a call to have this correct Ref. ***. On the same day the call was closed and no one contacted me to give me feedback. I then called the customer care line on the 7th May and I spoke to Nompumelelo who then informed me that the tariff is still the same. She couldn't assist me and transferred me to accounts where I spoke to Thokeba who logged 2 calls , 1 to have the tariffs corrected (Ref: ***) and another for a refund (Ref: ***)and I emailed her the contract which she accepted receipt of whilst on the phone with her. On the 10th may, the call for the incorrect tariff was closed (Ref: ***) and the 11th May the call for refund was also closed. On the 13th May I received a refund of R1991.05, which is less than what I should be refunded by MTN considering the ridiculous amounts I have been debited. On the 31 May I called customer care again to find out what is happening with my account tariffs if its been rectified and I spoke to Zama who then informed that I need to go to the store where the account was opened as the tariff is still not changed from what she could see. She also logged a call Ref: ***. This is absolutely ridiculous that I am being sent from pillar to post for something that was done from your side. How can I move from a R299 tariff contract to a R1700 contract. this is absurd and I demand to have this corrected and refunded what is owed to me. I spoke to 4 people already and this matter is clearly not being taken serious nor attended to , instead all the queries logged are just closed without even contacting me the customer to inform me of what is happening. this is disgusting service from you. I have been a MTN customer for years and to be treated like this is utterly disgusting. I demand that someone calls me and sort this out immediately.