Cell C personel shouting at me over the phone when I was quering about my contract that expired and I cancelled well in advanced

I had a contract that was expirind 1st of June. I phoned Cell C on 27 May well in advance informing them that I will not continue with the contract and that they should please do as needed to cancel the contract. They informed me that the contract will end End of June and that the last premie will be 25 June. At the end of June I contact Cell C for proof that the contract was closed. Then the call center person informed me that now I still need to pay for July. The call centre personel was un-professional and was shouting at me.This is *******. I did exactly as they told me giving Cell C well in advance notice that I am not extending my contract. I received a letter today that my premie will be lifted after doing exactly as I was informed and following instuctions exactly to close this contract. I WILL NOT PAY A CENT FUTHER. AND WILL TAKE THIS AS FAR AS POSSIBLE TO GET A LETTER FROM CELL C TO STATE MY CO TRACT IS CLOSED. I do have all relevant e mails and want all recorsings from Cell C to state state my case.