Today you have more and more options if you need to access several mobile phone numbers from one single phone. The first one that comes to mind is a dualsim phone. Very common in Asia and gradually coming to the rest of the world as well.
Yet there is something that is really bugging me with dualsim phones.The main idea of having 2 ACTIVE lines has been more and more castrated. Within a nice advertisement you will find a tiny hint telling you that the phone is "Dualsim Standby" . This defies the whole purpose of a dualsim phone, because you need to select the simcard you want to use and calls to the other sim card cannot go through.
And here is my point. Then you can as well use a dualsim adapter, because a dualsim adapter acts exactly the same and you are not limited by the most of the times lacking technical capabilities of a dualsim phone compared to its non dualsim counterpart.
The other thing with dualsim phones is that, once you have found a decent dualsim active smartphone, you will notice another disadvantage: No 4G/LTE capability. Best example is the new HTC One 8 Dualsim. It would be a perfect phone, but considering you are buying a new phone for over 600 USD and it cannot even handle 4G seems offside..
Of course you can argue that for you personally the dualsim abilty is more important than 4G, but spending so much money for not getting access to fastest data transmission standard still seems wrong to me. And to this day we cannot think of a decent dualsim active phone, that is technically comparable to latest single sim counterparts.