I have an AT&T SIM as my primary.
I was able to use USMobile (T-Mobile reseller), but it’s only good for 15GB per month, so only good in emergencies. They don’t officially support SIM’s in a router according to their chat line, but it says somewhere on the website that it works in GSM mode in a router and I can confirm that it does. A better method has been to simply Hotspot my T-Mobile phone, leave it always on, and connect to that in the Pepwave.
I also got a phone from visible.com and hot-spotted it. They limit to 5Mpbs for hotspots, but works well as a backup plan. I have the phone sitting next to the router. I haven’t really experienced any slow downs with it yet, even thought they do say they will prioritize traffic as needed since they are the budget extension of Verizon.
Not exactly a clean setup, but it’s working on the road so far. Way too many moving parts and I will trim down the services, but I wanted to shotgun approach it for the road to see what worked.
USCellular and Sprint are the only two I haven’t worked with.
Thanks for the input.