I have a Samsung Galaxy S4 Mini from Verizon (Model SCH-I435). My boss gave it to me since I needed a new phone and to my surprise, it was unlocked and I was able to get it working with ATT. My only problem so far is that the data speeds are not what I was expecting. I only get 2mbits/s when compared to my company phone (which is verizon) gets 10mbits/s. My thought was that the phone could did not support ATT's 4g/LTE network but from all my research, it looks like it should. When testing the speed or using data, it shows shows "H+" at the top of the screen.
Here is a list of supported networks from Samsung's website for the SCH-I435
Frequencies and Data Type Digital (CDMA/PCS)/1x, EVDO Rev A; Global(GPRS/EDGE/GSM(850/900/1800/1900); HSPA/UMTS(850/900/1900/2100), LTE (Band 13, Band 4)
Judging from wikipedia, Att uses band 4 and it says the phone supports band 4 so I do not get why it is not going faster. Any help would be appreciated.