Apparently, you can ask to end it but make all the line rental payments for the remaining how many months at once and then they will end it for you upon receiving the money you owe them. I did this the once with t mobile and am thinking of doing it with my o2 contract as i am sick of the poor service. Though the only thing is if you are going to pay the remaining line rental off to end the contract early maybe its worth just paying it as you go so u still can use up ur free allowances if you have any?