snowgum
2
Do you want to band-lock the modem so that only B1 and B3 are usable?
Or do you want to encourage active carrier aggregation so that B1 and B3 are aggregated?
If it’s CA you’re after, that’s something you have no control over, other than ensuring you’ve got good signal on both bands.
CA will get activated only when you’re making a significant demand for data, if at all.