Thank you for contacting Teltonika Crowd Support.
To configure APN on RUTX12 can be Auto/Custom APN.
The Auto APN feature scans an internal Android APN database and selects an APN based on the SIM card's operator and country. If the first automatically selected APN doesn't work, it attempts to use the next existing APN from the database.
An Access Point Name (APN) is a gateway between a GSM, GPRS, 3G or 4G mobile network and another computer network. Depending on the contract, some operators may require you to use an APN just to complete the registration on a network. In other cases, APN is used to get special parameters from the operator (e.g., a public IP address) depending on the contract.
An APN Network Identifier cannot start with any of the following strings:
it cannot end in:
and it cannot contain the asterisk symbol (*).
To set APN go to NETWORK > INTERFACES > MOB1SA1/MOBIS2A1 click on the pencil like feature and edit.
For step by step guide kindly check the following link on interfaces
For more technical support kindly revert.