I think that's only if you stay on the same exchange though isn't it?
And if you give it up then change your mind, you won't get it back. There's been a stop-sell on new copper lines for the last year and a half.
Some of them can be a bit of a tongue-twister.
There's been a lot of talk in the media about losing VOIP in a power cut, but the reason I want it is that I rate the reliability of the mains far higher than that of batteries. In the last 30 years we've had just one power cut, and I couldn't count the number of times I've been let down by various batteries in that time. A 999 call is a classic example of the type of application that batteries are least suited to unless they're float charged: rare, unpredictable, and urgent.