Question [Q] Unlocked Dual Sim Phones With AT&T MICROCELL?? (LIKE DESIRE 816 OR T2 ULTRA)

So I know dual sim phones work on att. I had a old note 3 clone. Worked fine on hspa+. But it would never connect to my microcell. However, the Droid dna, note 3 and galaxy s4 all for Verizon worked fine with my att microcell with my att sim. Even nexus 5.

I really want a HTC DESIRE 816 and thinking about trading my galaxy s5 for one. But I need it to work with the microcell. The only ones I can find are dual sim. So will they work? Anyone know?