Let me also point out that there is only one CO rep at the ORD B7 UA RCC. So if she takes a break or goes to lunch - then the desk is unmanned. So if the rep is not there - you will not be able to get a T-mobile card.
As I mentioned a month or two ago - I have an ATT premium plan account - old dial up with free WiFi at many hotel lobbies and airports (when airports charge for it). Works with T-Mobile using the dialer program and at many coffee shops that normally require a purchase to get a code.
My ATT account works at the ORD RCC without needing the T-mobile card and it works at the SNA UA RCC. The PHX UA RCC has free WiFi since the PHX airport has free WiFi.