Cancelled services but still got charged

I cancelled (01 July) Rain after numerous months of paying for nothing as the connection was bad and I indicated to their support that I cannot connect, to my surprise my account was debited on 01 Aug reasons I am given is that its a month to month and my sim was active. How do they keep sim active after i sent a complaint and said I am cancelling because I cannot connect and I have been paying for services not rendered. This is a ******* shame and I mean its tough times as it is and I just sponsor Rain with R479. Worse, answers i m getting are short and not helpful. I cant even call their line as it is not available.