Welcome to Vodafone Community
Was originally on Three and had a standalone Spotify subscription. Cancelled my standalone Spotify sub and changed to Vodafone and signed up to Student X with Spotify. Worked fine for about a week or so but today it suddendly changed to Spotify Free. FYI - I text the number before topping up with €20.
Mods wont be back until Monday to help. You could try live chat. To use live chat click talk to us at the bottom of this page then choose whether you're on bill or pre pay. It should pop up then. If Chrome browser acts up then try a different browser as some versions don't appear to play well with the links.
Can you advise what happens when you follow the below link on your phone over mobile data rather than Wi-Fi?