Cell c wrongfully debited my account

I received an SMS from cell stating that they are changing my debit order for my contracts from the last day of the month to the 15th. I immediately called them as I did not give them any intruction to change it. The agent told me he will escalate the issue because I told him I will not be able to pay that amount in the middle of the month. However cell c did not respond to me and then devoted my account on the 15 of August. This has left me with a huge shortfall to carry me through to the end of the month. I am left stranded and unable to meet some of my obligations because cell c wrongfully debited my account.