[AT&T LG G2] Scott:
Reflash ROM without wiping data.

International APN's for AT&T (Used in CleanROM XE)

<!-- ATnT for Non-HSPA+ Non-LTE device
<apn carrier="ATT WAP"
mcc="310"
mnc="410"
extraid=""
apn="wap.cingular"
user=""
password=""
authtype="0"
server=""
proxy="wireless.cingular.com"
port=""
mmsc="http://mmsc.cingular.com"
mmsproxy="wireless.cingular.com"
mmsport="80"
type="default,mms,supl,hipri,fota"
defaultflag="1"
preferapp="" />
-->

<!-- ATnT for HSPA+ device
<apn carrier="ATT Phone"
mcc="310"
mnc="410"
extraid=""
apn="phone"
user=""
password=""
authtype="0"
server=""
proxy=""
port=""
mmsc=""
mmsproxy=""
mmsport=""
type="default"
defaultflag="1"
preferapp="" />

<apn carrier="ATT WAP"
mcc="310"
mnc="410"
extraid=""
apn="wap.cingular"
user=""
password=""
authtype="0"
server=""
proxy="wireless.cingular.com"
port=""
mmsc="http://mmsc.cingular.com"
mmsproxy="wireless.cingular.com"
mmsport="80"
type="mms,supl,hipri,fota"
defaultflag="1"
preferapp="" />

<apn carrier="ATT Broadband"
mcc="310"
mnc="410"
extraid=""
apn="broadband"
user=""
password=""
authtype="0"
server=""
proxy=""
port=""
mmsc=""
mmsproxy=""
mmsport=""
type="entitlement"
defaultflag="2"
preferapp="" />
-->

<!-- ATnT for LTE device -->
<apn carrier="AT&T PTA"
mcc="310"
mnc="410"
apn="pta"
user=""
server=""
password=""
authtype="0"
proxy=""
port=""
mmsproxy="proxy.mobile.att.net"
mmsport="80"
mmsc="http://mmsc.mobile.att.net"
type="default,mms,supl,hipri,fota"
defaultflag="1"
preferapp=""/>

<apn carrier="ATT Broadband"
mcc="310"
mnc="410"
apn="broadband"
user=""
server=""
password=""
authtype="0"
proxy=""
port=""
mmsproxy=""
mmsport=""
mmsc=""
type="entitlement"
defaultflag="2"
preferapp=""/>

AT&T Stock ROM APN's (Used in CleanROM AT&T Edition)

<apns version="7">
<!-- ATnT -->
<apn carrier="ATT Phone"
mcc="310"
mnc="410"
apn="phone"
user=""
password=""
authtype="0"
server=""
proxy=""
port=""
mmsc="http://mmsc.mobile.att.net"
mmsproxy="proxy.mobile.att.net"
mmsport="80"
type="default,mms,supl,hipri,fota"
protocol="IP"
preferapp="" />

<apn carrier="IMS"
mcc="310"
mnc="410"
apn="ims"
user=""
password=""
authtype="0"
server=""
proxy=""
port=""
mmsc=""
mmsproxy=""
mmsport=""
type="ims"
protocol="IPV4V6"
defaultflag="2"
preferapp="" />

<apn carrier="ATT Broadband"
mcc="310"
mnc="410"
apn="broadband"
user=""
password=""
authtype="0"
server=""
proxy=""
port=""
mmsc=""
mmsproxy=""
mmsport=""
type="entitlement"
protocol="IP"
preferapp="" />

<apn carrier="Emergency"
mcc="310"
mnc="410"
apn="sos"
user=""
password=""
authtype="0"
server=""
proxy=""
port=""
mmsc=""
mmsproxy=""
mmsport=""
type="emergency"
protocol="IPV4V6"
defaultflag="2"
preferapp="" />

<apn carrier="LGE DEFAULT"
mcc="450"
mnc="00"
apn="qe"
user="lge"
password="lge"
authtype="1"
server=""
proxy=""
port=""
mmsc="http://203.229.247.19/mm1"
mmsproxy="203.229.247.28"
mmsport="8000"
type="default,mms,supl"
defaultflag="0"
preferapp="" />

<!--apn carrier="LGE MMS"
mcc="450"
mnc="00"
apn="tbt"
authtype="0"
user=""
password=""
server=""
proxy=""
port=""
mmsc="http://203.229.247.19/mm1"
mmsproxy="203.229.247.28"
mmsport="8000"
type="mms"
defaultflag="0"
preferapp="" /-->

<apn carrier="LGE entitlement"
mcc="450"
mnc="00"
apn="tbt"
authtype="0"
user=""
password=""
server=""
proxy=""
port=""
mmsc=""
mmsproxy=""
mmsport=""
type="entitlement"
preferapp="" />

<apn carrier="LGE 3G 2G ipv6 only"
mcc="450"
mnc="00"
apn="iv6"
authtype="0"
user=""
password=""
server=""
proxy=""
port=""
mmsc=""
mmsproxy=""
mmsport=""
type="default"
protocol="IPV6"
defaultflag="0"
preferapp="" />

<apn carrier="LGE LTE ipv4v6"
mcc="450"
mnc="00"
apn="lte46"
authtype="0"
user=""
password=""
server=""
proxy=""
port=""
mmsc=""
mmsproxy=""
mmsport=""
type="default"
protocol="IPV4V6"
defaultflag="0"
preferapp="" />

</apns>

All except the name of the APN is the same. Not sure why the defaults dont work for you. I wonder if some phones just pick up the first APN and stick with it?

Eitherway, next revision it will be broken out by official stock carrier APN so as to avoid any confusion.

EDIT: Also note that the AT&T Phone edition has LG APN's??? Strange?

Is LG filtering to the NSA? WTH? For real?