What is the best way to separately send messages trough different modem/providers ?

I have one SIM from T-mobile, one from Verizon, and when sending a message I want to tell it what modem/provider to use based on the receiver number format, so it will send SMS in it's own network.

From what I read, it is not possible to specify modem in the sendsms command, is it ?! Or specify modem in the file I can manually write inside "outgoing" folder ?

Is the "queue" and "providers" the only way to do this? Seems more complicated than it could be.