I dont think CL's phone was dual sim .. Going by Wikipedia Samsung produced them in the early 2010's
For me personally having to interchange sims would be inconvenient and fiddly allowing me to be only avail to answer calls when the relevant sim was in the phone
which is why a lot of people had 2 phones ie one for business one for personal use, before dual phones became available.
Im not sure what message the phone would give out to incoming callers or texters when the number they are ringing relates to the sim not in use either, so that might cause suspicion.
So for me 2 phones live at all the times perhaps one on vibrate/silent for discretion depending where/who the user was with would be the solution..
even more so if it costing me anything
I suppose the option depends on the person and the situation they might be in 2 sims would suit some people better.
But I think some personal details have to be given when purchasing a sim so that would be on record.
Just thinking through the possibilities thats all