Hi @Anonymous User
I thought you could change your surname details by going to My Account > Update Account, but reading the Account details under the FAQ it says you can't do it yourself and need to contact nowtv.
https://help.nowtv.com/article/change-or-update-personal-details
Therefore, if you are the authorised account holder on the account that needs updating, then I would suggest contacting nowtv live chat.
Open the link page below and click on the drop down arrow below Anything else to reveal the live chat button,
https://help.nowtv.com/get-in-touch/
