Sure thing, here's what I've got.
Name: ATT LTE
APN: PTA
Proxy: not set
Port: not set
Unsername: not set
Password: not set
Server: not set
MMSC:
http://mmsc.mobile.att.net
MMS proxy: proxy.mobile.att.net
MMS Port: 80
MCC: 310
MNC: 410
Authentation Type: blank
APN Type: default,mms,supl,hipri (I'm not sure if the order here matters) You can also try adding in "admin" as well.
APN Protocol: IPv4/IPv6
APN roaming protocol IPv4/IPv6
APN enable/disable checked and grayed
out on my phone
Bearer: unspecified
These were specified on XDA as the settings to use if you're coming from an S3(specifically with an S3 LTE sim, and data plan) Hope that helps!