Welcome to Vodafone Community
Do you use data much? Do you tether (use your phone as a mobile hotspot)?
What does your bill say about where the extra costs came from?
You cannot break a contract without buying the whole contract out. You have to either manage with the plan you have or upgrade your plan to manage it better at a slightly higher cost (but probably less then your current out of plan charges). Remember you voluntaryily chose this plan and signed a contract to agree taking it for two years.
If you private message (via the link in my signature) over the below info, I can look into this for you?
Date of birth:
Link to your thread or post: