Circlelife is using M1's infrastructure. Walls do block the signal, if his home is situated 'inside' a cluster of other buildings, or his room is not with window. Or sway sway that his spot is at the interference spot. There are actually signals booster inside commercial buildings that's why we are still able to get 4g inside shopping mall or office buildings. Download those apps where u can do speed test/signal strength check. I use Open Signal. It can do speed test, check signal coverage and even which cell tower u are connected to.