Then you just need an RJ11 to RJ11 cable of the required length.
BUT make sure it's specified as being wired straight as opposed to crossover. If it isn't specified, don't buy it.
Difficult to link to a specific product as links to retailers are prohibited on these forums.
Edit: I assumed you were asking because you needed a longer on due to moving the Hub? In which case a replacement from BT will just be the same as what you already have. Or is it damaged?
