It's very simple really. Stop paying and walk away. You aren't the account holder. VM don't care who is paying. Someone else is the account holder . Let VM chase them. Seriously that is all you have to do.
VM will stop the services in due course once the payments stop.
As you probably want to be a nice person you could write to VM here:
Virgin Media Sales Operation Support, Diamond Plaza, Daleside Road, Nottingham, Nottinghamshire, NG2 3GG;
and tell them what is happening.
Don't try and phone. VM won't discuss anything with you as you are not the account holder.
As for not caring about a credit record. Just wait and see what happens to your former house mate when they apply for credit and a default is seen on file. It will be an unpleasant surprise. And the debt collectors will catch up with them eventually. More unpleasant surprises.
I'm a Very Insightful Person, I'm here to share knowledge, I don't work for Virgin Media. Learn more
Have I helped? Click Mark as Helpful Answer or use Kudos to say thanks