TV bundle upgrade quoted one price, checkout showed another

Hi all, hoping someone can sanity check this for me. I'm on the Essential broadband and TV bundle with Nexora and got an email saying I can upgrade to the bigger TV pack for £6 extra a month. When I clicked through it jumped to £11 and then there was a one-off activation fee too. Is that normal or have I landed on the wrong page? I've tried twice now and it keeps changing at the last step.