How to set a cellular wifi dongle to prefer specific mobile network using AT commands?

I've been trying to solve this issue for a while and I've made several failed attempts.

TL/DR: I have a mobile wifi dongle that will be plugged into a router serving an unmanned kiosk. I need the dongle (with a Telus sim card) to prioritize connecting to Rogers roaming network. And this has to be a saved setting so that it remembers to prefer Rogers over it's native mobile network even after the device reboots due to power outage.

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Longer Explanation:

First, I had a Huawei E3372H-510 WiFi dongle with a Telus sim card. The location where the device would be used had a poor Telus network signal, but a strong Rogers signal and the sim card comes with unlimited global roaming. When you plug the device into a computer, it opens a web UI where you can manually select a mobile network, but it changes back to automatically selecting the default Telus network after a reboot. I was planning to use AT commands to change the default mobile network from the sim provider to whichever network happened to be strongest at each plant location.

For these Huawei dongles, you apparently have to flash the firmware to get it to respond to more than just the basic AT commands. I tried with one and got it to respond, but it was having connection issues as I only have access to region specific firmware that is not appropriate for North America. Tried to flash it back to web UI mode and I bricked it.

Now I have a Huawei E8372H-517, which is slightly better, but in web UI mode it still doesn't remember the preferred mobile network or recognize the AT commands I need to change the default mobile network. The only way I can think of to ensure it always goes to the right network is to use AT commands, but then I need a very specific firmware which is unavailable and every attempt risks bricking another device.

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Acceptable Solutions:

- Any repeatable method to set a preferred mobile network on a wifi dongle

- If there's another device I can use instead, I'm happy to switch

- Whether it uses AT commands or not is irrelevant, I just need something that works consistently

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I'm out of my league on this one and there's no one else on this project that can assist, so any help you can provide is much needed and appreciated.