Att has great internet service in Denver what are you talking about mobile is the one that's horrible theyr coverage is spotty I hate that but does the nexus 4 for tmobile get hspa+ with att?
no putting in the sim really wouldn't make any difference at all but I am having the exact same problem with my droid dna and my htc one x and ive been trying to find some answers for a while now ill let you know if I find anything