Backup calling when both SIMs are online

I have 2 SIMs: The first one has only data and can't make calls, the second one can make calls but doesn't have any data. With the "backup calling" feature, I can make and receive calls over the cellular data of the first SIM if the second is offline. This is useful for me because my phone doesn't have dual SIM dual active so cellular data stops working if I am making a call. Backup calling requires the phone calls sim to have no signal which I can force by limiting the SIM to 5G. Obviously doing this is not ideal as the phone searches for 5G signal, can't find it and drains its battery quickly. The weird part is the phone supports 5G and so does the carrier, my account (?) doesn't support 5G because I don't have any plans on the SIM. Forcing 2G or 3G won't work, those are still available where I live.

So is there a way to use backup calling without taking one of the SIMs offline? Or is there a way to take 1 SIM offline without making it search for an unavailable band? I don't want to lose cellular data each time I receive a call or drain my battery quickly.
Phone is Galaxy A34 5G running Android 14, not rooted