I bought an unlocked iPhone 7 (MN8L2LL/A) for use on AT&T back in 2016, and gave it to my wife last year when I upgraded to an iPhone X (MQAK2LL/A). In January, we switched to T-Mobile and for the most part, service has been relatively solid for me save for a few dead areas (more dead spots than AT&T, that's for sure). But my wife's phone often gets horrible service -- even if we're standing side by side. I'll have full bars and service, and she has nothing. Does her iPhone 7 simply not have all the bands necessary for T-Mobile service, or is is potentially a factor of modem performance (I don't know whether our phones have Intel or Qualcomm modems). If it's truly a problem with a lack of bands, I have no problem getting her a T-Mobile iPhone 8. But I just want to make sure that I won't have the same problem if I buy her a new phone. Can anyone be of any assistance as to why her experience on T-Mobile is so much worse than mine -- even when in the same location?