Samsung Galaxy S7 Duo no longer supported dual SIM operation

[navionics]

I have been trying to find the answer why the S7 no longer useable as a dual SIM phone. As of recently, AT&T has decommissioned the 2G towers and with that dual sim operation is out of the picture. Since S7 Duo can have only one SIM at the time on 3G or hire, and the other automatically downgrades to 2G. I wander if new Samsung software would allowed both SIM's to operate on 3G

Any input is highly appreciated