MTN bad service

I Upgraded to a MyMTN Home Uncapped FLTE 10Mbps contract on 8/11/2021. My account no is BA***. The upload and download speed is not as per the contract 10Mbps. I have tested it over a period of a few months. I reported it to MTN Coverage and they send a MTN representative to check my claim of slow speed as there are suppose to be good coverage in the area. H confirmed that the speed is low and gave me a REF No ***. I am very frustrated as I have been trying for several days to cancel the contract. I went to the store in Edenvale where I took out the contract, SABC2299 MTN STORE – GREENSTONE SHOPPING CENTRE L073 – EDENVALE and they told me that I cannot cancel the contract with them, I have to phone 135 and cancel it myself. I had the router with me when I went to the store. I have tried the 135 number 9 times today. Four times I get through to a MTN CHAMPION that told me they would transfer me to the correct person to help me, only to be cut off. I don’t know what to do next to get this contract cancelled. Very frustrating