No, it will NOT connect to ATT 4G LTE, only ATT HSPA+. Tried different phones and sims, even took phone to regional ATT service center. Tech said if it's not an ATT branded phone, it won't connect to LTE in this area. (NoVa/DC). Back at BestBuy, tested 2 S7 phones (unlocked vs ATT) using Speedtest by Ookla, unlocked S7 connected at H+ only achieved 7mbps down. Swapped sim to ATT S7, it immediately connected to LTE and achieved 30+mbps down. Network speed is more important to me than bloatware so I returned unlocked S7 for ATT S7.