Unprofessional service and billing problems

Last month I moved my salary to my savings, not aware that one debit order did not go through. I quickly went to pay my cellphone contract as I didn’t want to be behind. I am now billing R200 + for rejected debit order. I called Telkom billing and this gentleman told me that the reason why my bill is so high now is because of the debit order bounced. I then asked him to point me in my contract where it stipulates that I have to pay that amount and he couldn’t, instead he refers me to the website. We already struggling financially but these companies are not helping in anyway, I pay for my phone in time, not by debit order but I still paid. Why am I charged still? I have stopped my debit orders until someone shows me in my contract where is says I need to pay for that amount, I don’t mind paying but R200+ is a *******