Just wanted to document a quick issue that we just troubleshooted. One of our users was using a Hologram SIM in a SixFab V1.5 GSM/GPRS shield on their Rasbperry Pi. They were having some issues connecting to the network and we eventually boiled them down to having to run the following commands to ensure that the shield was able to open ppp sessions.
sudo route del default
sudo route add default ppp0