I have a Lumia 1520.3 on Straight Talk. (Yes, the 'unicorn' version does exist, it is available for ~$500 at B&H Photo and Video in all colors)
I recently got Straight Talk with the BYOP kit from Walmart, but I derped up and chose the T-Mobile network version of the Nano-SIM. After I found out that the ATT version is far superior, I transferred my service to that SIM card. However, the APN settings that worked with the T-Mobile version don't work with the ATT version, so now I need the correct APN settings for my new SIM card.
I recently got Straight Talk with the BYOP kit from Walmart, but I derped up and chose the T-Mobile network version of the Nano-SIM. After I found out that the ATT version is far superior, I transferred my service to that SIM card. However, the APN settings that worked with the T-Mobile version don't work with the ATT version, so now I need the correct APN settings for my new SIM card.