Yes CDMA at a lower freq does penetrate buildings better then the higher freq GSM, Ive been in wireless for years and when I worked for at&t in a large town in the west we actually had to ask/beg a major mall to install repeaters or some other gadgets in the mall just so our phones would work, Verizon had no problems nor did sprint, which is puzzling because Sprint used pcs at a high freq, but it still worked who knows maybe they had something installed in the mall to, AT&T and Tmo sucked. I also heard this from our guy who worked on the towers about 5 years ago..CDMA is a newer more advanced technology then gsm as well
and yes I am aware of wi-fi calling with tmo, but I dont have internet in my apartment i have being using tmo's hotspot, thats another reason im so upset with them because my bill is $112 a month and I can only use my stuff about 3/4 of the time id like because the rest of the time my phone is searching for signal or tripping out