Free prepaid 'Sim card"

I got a call from a mrp mobicell call centre agent asking me if I received a free sim card loaded with R25.00 airtime which is also free and if I needed more airtime I should load it myself and will be billed for it and it is not a contract and only when I need airtime I should fill it in. I said ok. I then decided to go online and find out more only to find out I will be charged for the airtime on a montly basis. I think this is very misleading and something should be done about it because I read that a lot of people got billed and had to pay the money. all our personal information should not be given to other departments of the group. if we have milady account, Mr price or mrp mobicell should not contact us with false information. Please look into this. there are a lot of people who don't have money and have to still pay for things that they don't use.