Canecling contracts with cpw's complete insurance is perfectly legal. (Only store staff are not allowed to promt you to cancel). However if you want to break the contract early you can anythime after 9 months (used to be 6 months but it changeD in august o7) its fine, You dont even have to give them a reason.

Just pay the excess and lifeline (cpw insurance company) will settle the remaining line rental. Bear in mind you will lose your mobile number.