How to select a specific carrier

I have two nova modems. One has been mostly stable for a month. The 2nd I just setup today is very slow. When I try to ssh in via space bridge it hangs. If I ping out from the host (ping -I ppp0 8.8.8.8), then the inbound ssh starts to work again. I have to keep pinging out from the host for inbound traffic to get through.

The only different between my two systems (two systems with one modem each) is the stable system is connect to Verizon, and the unstable system ATT. Is there a way to force the carrier so I can test if this is the source of the odd behavior.

Thanks.

P.S. I took this out of the box and just setup PPP via linux (not hologram python code). This is how I run the other system. I am using the chat script however from the python code.

P.P.S. right after posting this the modem disco’d for the Nth time and reconnected (this time with Verizon) and now it is as fast with low latency and stable as modem 1. So, now I would really like a way to force this. Thanks.

Are both modems the R410 version?
We don’t have a command in the SDK to do this, but if you open a terminal to the modem you can do AT+COPS=? to scan for networks and then use the AT+COPS command again to select a specific one.
You can see more information in the UBlox AT command manual: https://www.u-blox.com/sites/default/files/SARA-R4-SARA-N4_ATCommands_(UBX-17003787).pdf