Further inquiry on device compatibility:
We have replaced the SIM cards that came with our field devices (Netbiter) with Aeris 2G/3G cards and have been successful for most sites. A few have not worked well. The original OEM SIMS did work and this is the compatibility info from them:
"The netbiter is not supported by the Verizon network. The modem on the Netbiter is GSM 3g with support for 3G/UMTS (WCDMA/FDD): 800/850, 900, 1900, 2100 MHz
In the united states you should be able to use AT&T or T-Mobile for main operators."
I'm thinking this is a frequency issue? We have tried both ATT and T-Mobile SIMS from Aeris and are successful with that most of the time but not always.
Thanks for any advice you can offer.