charged almost same price for 25g as uncapped

im really not happy with my first bill. i was charged r745 for 25g of data how is that fair why was i not given the option of paying r300 to be uncapped from the start? why was i not fully informed of this if I knew it was going ti cost that much i would have only started my contract on the 1st of june. i also app**** way before the 9th for the contract. im really unhappy ********** 164