I am having a similiar problem, I click on the link and it says not available while on wifi, my wifi is off and I do not have wifi available where I am located, which is why I need a data service pass to begin with.
when I select the option of purchasing a service pass I get a notification saying not available to purchase over WiFi , my wifi is off also I do not have wifi available at my house at all so pls how do I purchase a service pass