Thanks for your post and welcome to the forums. It's really great having you on board with us in the Community.
As mentioned by jb66, the blue light card discount is only for new customers. The account would also need to be in the card holders name.
Speak to the team on 0345 454 1111 as we'll always try to see if there are any new discounts or promotional offers you can benefit from as an existing customer on your current services but sometimes, to get the cheaper deal, it would mean changing part of your package or downgrading part of it to make the price lower.
Let us know how the call goes and what you decide to do.