Rudeness from staff

I have a debit order with Telkom which needs to go off on 25th of every month. October, Telkom debited late and unfortunately the debit order was returned. I immediately went and paid my invoice amount in cash. On receipt of my invoice this morning I am charged R202.70 for the debit order that was returned. I called to query as I immediately paid what was due. I was told that returned debit orders get charged for. I then requested my Debit Order to be cancelled. I was told it is done. On requesting proof thereof in writing, I was told by Fikile that they do not have access to e-mails??? A telecommunications company whose staff can't e-mail??? All I want is proof in writing that my debit order is cancelled and that the last debit will be on 25 November, Is that so much to ask??? Instead I got told nonsense and got a bad attitude from the call centre agent