hotspot

Has anyone figured out how to successfully get the Mach-E to connect to an iPhone hotspot? My phone shows up in the WiFi list. It starts connecting. The iPhone shows something connected. After 15 or so seconds the car gives up (never finished connecting) and the phone stops showing any client...

I was under the impression that I could add the MME as a "device" to my T-Mobile plan, sort of like I'd add an iPad. Is the car only able to register with AT&T?