day light *******

In November 2013 i took out a contract on the internet for my little sister for her birthday in December and all was well until i went to a branch to enquire as to when iam due for an upgrade and i was told to come back after the 26 of November and i went and took a contract and was supposed to pay R 230.00. Imagine my shock when i realised that vodacom was actualy charging me 309 and their reason for doing this is that according to them i took my first contract in February 2014 which is a lie and that i was only supposed to upgrade in February. How is this possible or is it just another way for Vidacom to just rob its customers blind? I am realy angry because Vodacom is lying inorder for them to take my hard earned money. The people in the branch just say to me there is nothing we can do because its people in accounts who are responsible. Can someone please give me an answer that is valid.