Overcharged

On Saturday I received my statement and was shocked to see that it was high. I saw it was stated that I had purchased content. Upon calling I was told the very same thing but to my surprise I've been with vodacom for over 6 years and I've been accessing the internet but have never come across such nonsense. I must say I'm extremely annoyed and disappointed, the only thing keeping me is the fact that it's a contract otherwise I would've chewed and threw the Sim card away. If this nonsense repeats itself and content is purchased yet I know I didn't subscribe to anything I'm going to take things further