After calling T-Mobile and configuring APN, I can now get 4G. However, I still can't tether. The T-mobile rep said I am out of luck and can't tether with stock tethering application, because it's looking for AT&T servers.
I just got this ZTE warp 4g N9510. I just finished rooting the phone. I am having a problem with the protocols for the wifi tether prog http://code.google.com/p/android-wifi-tether/ . I can't get my laptop to see the ZTE wifi hotspot even when wifi encryption is completlly turned off and the phone is an open hotspot. My old phone a Kyocera Hydro had no problem running the wifi tether prog.