"Tello UK services are no longer available."
Looks like they shut down operations in the UK at the end of 2017. At least it seems like it isn't affecting Tello USA. I wonder why Tello UK didn't last?
I wonder, too. Perhaps--www.1pmobile.com/tello/---the company the Tello is helping members to migrate to, had something to do with it. Also, after a brief glance at teleco prices in the UK, which appear to offer more for a little less than in the US, maybe price competition made it more difficult for Tello in the UK. Then, there is also the Sprint service only thing, assuming service on Sprint was Tello's only offering.