Vodacom contract @ Afrizon

Hello My name is Kagiso, since i took a cellphone contract with afrizon vodacom they haven't deducted their monthly subscriptions the only thing they deducted was R120. 00 with is the pro rata i am guessing but not the R289 that which agreed upon,and the airtime they said i will get is about R210 but i have about R642 i don't understand how .....please help with why they not deducting i don't want to find myself with arrears i didn't cause as i have other commitments