When configuring a new Teltonika modem, the only thing you have to set to get it to work is the APN.
For AT&T SIMs purchased From ISP Supplies
For Verizon SIMs purchased from ISP Supplies
A complete list of APN's we know of is HERE.
For a complete HowTo guide, watch this YouTube video:
If you want to integrate your devices with RMS, the Remote Monitoring System for upgrades, configuration changes and monitoring, see this video with an introduction to Teltonika RMS: