Error "Uh-oh, it looks like we have our wires crossed. Please try again later."

I have the exact same issue.  I live in a rural area and wanted to try out the service first for internet before making any drastic changes.  Not able to link my Home Internet Gateway device phone number. No one at T-Mobile has any idea of what I am talking about, when talking with tech support they disconnected me and never called me back.  It took me over an hour on the chat box just for them to tell that at least I could pay my bill through the app using the “pay as guest” button.  Perhaps this issue is more pervasive than they want to let on.

Any suggestions or resolutions will be apprecated, otherwise, I will have to say goodbye to T-Mobile until they resolve this issue.

Thanks.