Pathetic service

I have never been so patronised in my life. So about a month and half ago i called mtn call centre asking when will my contract end ,then the gentleman said it ends on the 06th July so i must call on the 7th to cancel the contract and my number will go prepaid.... i then called again on the 6th to cancel and then again advised to call on the 7th ...which i called on the 7th to cancel. The agent told me he requested it and my phone shod be prepaid within 24 hours. ..... then BAM today i get my monthly airtime again nevermind the fact that i wanted to cancel the stupid airtime. . I then call again and the agent tells me about a 30days notice like how do people do that after u tried so hard to cancel the contract......Can i get assistance i cancelling this thing ASAP