Can I assign specific devices to connect on a specific band?

I have DSL and the ATT supplied Arris BGW210 dual band router.  For some Amazon Alexa connections (ie multi-room speaker application where audio plays simultaneously on multiple speakers throughout the house) or casting my Oculus Quest VR headset to my TV I need certain devices on the same band together for components to communicate properly.  I spent over an 2 hours on the phone with ATT tech support and they said they couldn't do it.  My options were to have them disable one of the channels and re-connect the devices that were on that channel so they would default to the remaining channel when re-connected, or just try repeatedly disconnecting and re-connecting the devices in hope that it would connect to the other channel.  Does that sound right? ...because that just sounds nuts to me.    

There is a purpose to having a dual band router - one channel for distance and the other for speed.  So disabling the 2.4GHz (distance) is gonna matter due to the location of the router and the configuration of the house and possibly leave us with dead spots due to range.  I don't wanna disable the 5GHz because I want the speed for streaming and gaming. The names of the channels have to be the same and the passwords have to be the same, because I already thought about renaming one of them so I could direct to which channel devices connected, and the online controls wouldn't let me.  I've identified which devices are on the "wrong" channel and just don't know why I have no control over channel assignment.   Anybody have a solution?