Feel Cheated

I was a loyal customer of Virgin Media for years. This year ,since their price increase I decided to quit.i called them in December 2015 as it is the month that I usually call to pay my line rental up front so that my monthly debits are not too loaded. I called and asked to end my contract . A rather arrogant woman said that I can only end my line rental payment as the contract was this time for a period of 18 months and ended in July 2016. She said I would have to pay a penalty of ?120 if I wanted to end the contract . I could not understand how the contract for the line rental was in December and the contract for the package was in July 2016. This means that I would have to pay much on my direct debits from January to July 2016. She was not even sure about how much I would have to pay monthly for that period as she kept making mistakes when I asked precisely for my instalments . I felt cheated