Vodacom
Incorrect data bill

I opened a smart lite contract costing R135 pm and i took a nokia lumia 610. i was given free data and whenever i over use it the bill would reflect immedietly on my account and that amout would be deducted. on the 1st of January i recieved a bill stating that am owing R2400. I continued to pay R135 and stopped using the data sim but in March the bill came stating that am owing R3400. this amount is incorrect. am a student and there is no way that i can afford this amout given that the charges are incorrect