I have a complicated and specific question.
Is it possible for AT&T band 12 B and C blocks to interfere with T-Mobile's band 12 A block?
This is the scenario behind the question: One of my favorite vacation places is the Pennsylvania Grand Canyon. My retired aunt and uncle have a cabin near a small town called Oregon Hill that I often visit. There's a big T-Mobile tower approx 10 miles North-Northeast in a small mountain top town called Antrim. I get about one bar at their cabin from this Tower. AT&T only has 3g 850mhz service at my aunt and uncle's Cabin. My father is a member of another cabin, and the same Tower is approx 16 miles northeast from this cabin. This cabin is about 200 yards from the top of the mountain, and if you walk to the top, other than leaves from the trees blocking you, you are directly within line of sight of that Tower. At the top of this hill AT&T has 1-2 bars of LTE coming from a tower who-knows-where. I am on a T-Mobile Galaxy S7, and when I go into my service mode info page through the dialer app my phone shows that it detects the T-Mobile tower with strength around -100 dbm. The tower that my phone dectects has the same physical cell identity as the tower in Antrim, but it cannot connect to it. After about 30 seconds of saying no service and showing in the service mode app that it is detecting the tower at Antrim, the physical cell identity changes for a few seconds, displaying the physical cell ID of the AT&T tower, then everything goes to emergency calls only on the AT&T tower. Even if I go to the network operators section in settings and do a network search, T-Mobile comes up, but when I attempt to select it says unable to connect to T-Mobile network. (This all happens at the top of the MTN near the 2nd cabin)
The more complicated question is why am I able to connect to the Tower in Antrim at my aunt and uncle's cabin, without a direct line of sight to it, and at the cabin that my dad is a member of I cannot connect to the tower but we do have a direct line of sight to it.
The same thing happened when I used a Moto x pure, and iPhone SE in the same locations.
I apologize again for writing something so long, but hopefully I provided as much information as possible.