If you are changing broadband providers you can normally choose to keep your phone number.
It’s not a difficult thing for ISPs to do, especially if your old provider and your new provider both use the Openreach network to give you broadband.
So even if you’re changing from Sky to TalkTalk, or BT to Plusnet, you should be able to keep your phone number.
Just ask your new broadband provider and they’ll help you through the process.
The main exception is Virgin Media. They build their own cable and fibre networks, so if you are switching from an Openreach broadband connection to Virgin, your phone number will need to be transferred to the new network.
Simply tell Virgin that you want to keep your number when you sign up for a phone or broadband deal and they’ll take care of the rest.