contract a farce

Ive taken out a contract for my daughter. The package that i took was for R399. Ive been with cell c now for the past 4 years. I have 3 contracts with cell c. Well since i took the new contract out in september 2014. My daughters account is over a R1000 per month. Ive put a cap on her phone of R100. Because that is all i can afford. When i took the contract out i sighned for 700 mb 100 sms and 100 minutes talk time. When my daughters mb gets done cellc gives her the free will to buy extra mb. I phoned and asked them to put a cap on her mb but they said they cant. I feel its a total *******. This is where cell c makes . But since the new contract in sept where she has the access to buy mb anytime . I feel this contract is getting out of hand . Ive never payed so much for her contract the past 2 years. I feel its cell c fault that i have to pay alot every month because they are unable to put a cap on the data. I demand my money back . It is against my statutory rights as a consumer. I fight with her every month. Ive taken her cell phone away. I feel im not in control of that account anymore but cell c is. Cell c failed to tell me that no cap can be put on the data.