Cancellation Issues

I had an issue cancelling my account. I spoke to a Telkom representative who gave me an e-mail address to contact a calendar month ahead of time. I politely requested that my internet service be cancelled but the line kept as I would like to use another service provider for internet.

Our internet was cut months later as I found out that our internet subscription was not cancelled and the account being debited from would then have had too little in it for the internet service and the line.

I contacted their customer services who explained to me that I didn't attach the necessary cancellation form and therefor my e-mail was not valid. I feel like it was unfair that I was told that my e-mail was invalid now and nobody had even bothered to reply to my original e-mail. Had anyone said anything at the time, I wouldn't be months in arrears and I'd be able to reactivate my line. My e-mail was clear enough and I feel like someone from Telkom's end should have responded and told me my cancellation request wasn't valid.

Am I crazy for thinking that's fair?