Refusal to cancel data contract

I have been trying to cancel my data contract for the last 2 days. Yesterday the call center agent refused to take my cancelation notice as he said I was 1 day too early. Now I am trying to phone keep getting put through to upgrades and when I ask for cancelations department I get cut off. I have had enough of Cell C and will never use them again for any reason. I want the contract canceled and no further debit orders to go off my account