I'm not sure if the phone was a bit confused switching back from CDMA to GSM (the Nexus 5 is one of the few phones with both radios) when I swapped Sprint's SIM for T-Mobiles, but the phone simply did not see any networks with the T-Mo SIM installed, even after multiple resets. Strangely enough, my sister's AT&T SIM worked with no problem. I suppose if I went to the AT&T store first I may not have gone with getting a new phone. But by that point I was starting to come around to just accepting a big phone after all (which really started this mess in the first place). Plan works out to about what I was paying at Sprint, the service actually works (I have 4G everywhere in my house, plus wi-fi calling locked in) and I've got a current generation phone.