Incorrect contract term

In December 2020 I decided to have my mtn contract upgraded I visited the mtn gateway umhlanga branch the one near CNA I chose a tablet deal for r299 I was advised it's a 24 month contract however on the brochure it stated 36 months the sales agent advised me that it was a mistake and that it was indeed a 24 month contract I still wasn't convinced but the sales agent assured me it's a 24 month contract and gave me her word I agreed and did the upgrade weeks after doing the upgrade I went back to the store and I was shown my upgrade and it had a reference number for a query that was logged in January I returned back home In the Free State in February I decided to do a follow up I called 135 and I was advised I'm on a 3 year contract and I explained the call centre agent about my issue I was told to call the store that did my upgrade sadly to date I have failed to get hold of the branch the phone just rings with no answer this is absolutely unacceptable for a business to not answer calls I have been a customer with mtn for more than 8 years and after experiencing this issue I'm not confident in them anymore I will be taking this matter up legally