Don't worry, no changes have to be made to your own phoneline. Nobody will need to visit your house to play with your phonelines. BT have upgraded their telephone exchanges to use Broadband, which means almost everyone can now access it.
All you need is a Broadband modem, which your supplier will send you, and what's called a DSL filter, which plugs into your phone socket and allows you to use the phone and the Internet at the same time.
Once you go on to Broadband, you'll wonder why you didn't do it sooner!