I just signed up for a month to month contract with mtn

I just signed up for a month to month contract with mtn. (Less than 15 min ago from publishing this review) I get a contract stating that my billing date is the 15th. Yet i did the sale online on the 30th. I was already chraged a prorata rate. Infact as mentioned the sale was done online so i paid immediately. How! I havent even received the hardware, the order wasnt even confirmed yet. But im expected to pay another full month on the 15th. ******