(From public article)
Changing APN for T-Mobile and multi-carrier SIMs such as Twilio, Teal, Hologram, etc.
Note: Changing APN for AT&T and Verizon requires additional steps. See instructions at bottom of this page.
Step 1
Connect gateway to ethernet.
Locate the gateway’s IP address (you can use an IP scanner).
Get gateway’s password, which is the serial number on the sticker on the bottom of the gateway.
SSH into gateway using a command line interface program like Terminal on Mac or Command Prompt on PC:
ssh root@192.168.2.xxx
Password is the gateway serial number.
Enter following commands to check the system version, current firmware, and current APN:
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Changing APN for AT&T Sims
Step 1
Open FileZila Download and open FileZilla and connect to the gateway with host being the IP address of the gateway, “root” as the username and the Serial Number of the Gateway as the password and the port which the gateway is on.
Step 2
Go to the dev/shm in FileZila FileZilla and input these two files in the shm folder.
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