Nothing brinen really. I just need help with something specific

So I can get some of my devices connected (online) because some of my devices all of a sudden switched to the 5G network from the 2.4. Like the phone got on the 5G and maybe a couple of othet things and then some I had to put the password I. For them to get online on the 5G. But I still have devices like a Yale door lock/bridge  and 2 outside security cameras that aren’t working. I found out it’s because they will not use the 5G. I tried to go back in like I was encouraged to do and get my phone temp onto the 2.4 just to be able to connect those and then  they’d work on that and my phone could go back on 5G. . So  since zoning my own Arrus Modem which is a SBG8300, my internet company was not able to do much for me. They said I needed to contact Arris and tell them that I needed to have the 2.4 and the 5 two separate things, and I which accidentally clicked out of that chat and forgot the exact tech terminology. Something about they would need the gateway and the password. That what I need help with. It’s driving me bonkers and taking every ounce of my time and more. Thanks if someone can help. I wanted to talk to a live person tonight, like NOW,  but I could not figure out how to.  Too many fake things out there etc.