THE telecoms regulator has banned so-called "rollover" contracts - which trap more than 1m BT customers with their landline provider - following a Daily Telegraph campaign.  The year-long contracts renew automatically without the customer having to opt in to them, and consumers are then charged to leave the provider. Ofcom said yesterday that the contracts "raise barriers to effective competition by locking customers into long-term deals with little additional benefit".  The contracts for both landline and broadband internet services will be banned from December, while those who have already signed the contracts will have to be moved over to different deals by December 2012.  BT is by far the largest provider of such contracts - with an estimated 1.5m customers on rollover deals - although other providers such as TalkTalk offer rollover contracts to businesses.  The Daily Telegraph has campaigned against rollover contracts, and wants to see them banned f