Telkom need to credit my account

I have a contract with Telkom. I pay R288 monthly on the last day of the month as per our agreement. On the month of May the last day of the month was on a Sunday and that's when i got paid on Sunday. Telkom didn't debit i thought they where going to double in June but they never did they took the usual R288 and blocked my account saying that I'm in arrears. I went to the store and paid R290. Yesterday i received an sms saying that my balance due for the month of July is R488.07 i called Telkom to ask about the R200.07 extra on my account they told me that its penalties. I don't understand where the penalties come from because the funds where there on the agreed date which is the 31st of May. The consultant told me that they don't do the debits on a Sunday, my question is why didn't they do it on Monday then why must i be the one incurring the costs of them not debiting on the agreed date that was on Sunday why didn't they do it on Monday then because they are the ones who failed on the AGREED date. Ok the failed in May why didn't they double in June because the funds where there in June instead they did an unpleasant thing of blocking my account and i had to go to the store and pay for May but in July they telling me that i need to pay R200.07 in penalties. Why??? Why must i be the one bearing the costs for their failure like the whole R200 extra thats like another device . Telkom must just credit my account with those penalties i can't be paying penalties like i didn't have funds available on the agreed date. As if them blocking my account was not enough, that was also unfair because it inconvenienced me for the whole 2 days because they said payment made in store takes about 2 days to reflect. No i am not happy with the way telkom is treating me now. All other debit orders went through on that day and the last ones went through on Monday. I don't owe telkom anything but nows i have to pay R200.07 in penalties thats madness.