Thanks for your post and welcome to the Community Forums, Natalie2021,
A landline is not needed for your broadband service to work since it's a cable-based and not a phone-based service. Any of or services can be had by themselves, independently for example on our page there is a section marked broadband only https://www.virginmedia.com/shop/broadband/broadband-only
However your services are bundled together to give better value for money, changing the bundle may increase your overall package pricing. Unfortunately we are not able to process upgrades, sales, cancellations or any package changes here in the forums as these require a dedicated team to manage these changes.
Cheers,
Corey C