Wrong amount

I joined cell c last month in d form of a router contract, barely a month later dey Givin me problems. My package is 20gb per month, 10*anytime 10*nightowl. I paid the subscription fee of 199 month end n dey supposed to bill 199 every month on the 15th, now this morning I receive a bank sms of a deduction of 308, Dat is not our agreement. Cnt get through to da ryt ppl to sort dis mess out. I need my money back, solve it