Just be careful and check with your current provider (Talk Talk) because things have changed, what the last 2 guys are saying may not apply to you, it did not for me.
My old supplier, Vodafone was using the old copper line for their FTTC , fibre to cabinet service and the phone line was bundled together with that.
When I cancelled the broadband with 30 days notice, yes the internet went down but so did the landline at the same time. If you don't cancel it with them it will keep going...there is no PAC or MAC code...you are paying for a totally different type of service to your sim based, home broadband. You may end up, as I did, with 2 wifi networks for a month...which was useful as I had an issue with the original, 3 router,
This is the way things are going. Nobody wants to supply landlines anymore, except BT...unless you are taking the broadband as well.