You are not swapping the accounts toa new property, you need to ask to move Now broadband to the new address if you are the bill payer, see here :
https://help.nowtv.com/article/how-do-i-move-now-broadband-to-my-new-home
Do not mention swapping accounts, as that is not what is happening and that will only confuse things, read what it says in the linked guide and that is what you need to do
