That's my very point. Like you, I don't see why it should increase - which is why I'm saying that I hope (for the sake of others)that it doesn't.
It's simple enough to check, you just need to type in your postcode, to a broadband fibre comparison site, to see what's on offer locally, and the cost.
I think I'm correct in suggesting, that VoIP phone calls seem to be quite a bit more expensive, than the deals you could find with a copper line. Our £3 pm deal, does include (I think) UK calls, after 6pm, but we make not use of them, we just use the free anytime, on our mobile contracts, it's so much simpler.

