I'm using my T-Mobile LG G2 on Straight Talk (on the AT&T Network) and got data after creating an APN with Straight Talk's settings. To get LTE I also changed System Settings -> Tethering & Networks -> Mobilie Networks -> Network Mode to GSM / WCDMA / LTE auto (I previously had it to WCDMA since my previous provider did not have LTE). For AT&T I found this: http://www.att.com/esupport/article.jsp?sid=KB424489
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