Miway debited my premium on a date not agreed upon

I can not contain the amount of rage that I am feeling right now. Yesterday on 20/12/2015 I received an sms from Miway stating that they will deduct my December premium on 21/12/2015. This alarmed me because my agreement with them states that my premium will be deducted at the end of the month because that's when I get paid. Imagine my horror when I call today 21/12/2015 to enquire about this to find that they had indeed gone ahead and deducted my premium without my authorization. To add insult to injury my account has insufficient funds and I will thus incur bank charges because of Miways ********* practices and the lady who \assisted"me (her name is Dikeledi) didn't seem to care in fact she sounded like she found the whole matter amusing. I am disgusted with the service that I have received from them"