Why can't I use two SIM cards and one microSD card at the same time?
You might experience that you can’t use two SIM cards and one memory card at the same time in some Xperia devices. This is because the hybrid SIM tray/trays that is used in these devices only allow you to either insert an additional SIM card or a memory card.
The hybrid SIM tray occupies less space. If you want to use two SIM cards, it’s not possible to expand the storage of the device using a memory card.