Currently, Xperia® devices support DSDS (Dual SIM Dual Standby), which doesn't allow two calls on two different SIM cards, but allows you to forward calls that come in on SIM card 1 to SIM card 2 when SIM card 1 is occupied and vice versa. This function is called Dual SIM reachability.
About Dual SIM Dual Standby (DSDS)
DSDS devices work with one or two SIM cards inserted. You can receive calls and messages to both SIM cards. Before you can use the SIM cards, you have to enable them in the Dual SIM settings menu. Only one SIM card can handle data at a time, and you can select which SIM card you want to use.
You can select which SIM card to use for making calls or sending text messages (SMS). When one SIM card is engaged in a call, the other SIM card is temporarily disabled. This means that during a call, only the active SIM card is available for communications. To receive calls going to the disabled SIM card, enable the Dual SIM reachability feature to forward calls to the active SIM. Once Dual SIM reachability is enabled, you can put the ongoing call on hold and answer a call forwarded from SIM 2 to SIM1.
Enable the two SIM cards
- Make sure you have inserted both SIM cards.
- Find and tap Settings → Network & Internet → Advanced → Dual SIM.
- Drag the sliders beside SIM1 and SIM2 to the right.
Enable Dual SIM reachability
- Make sure you have enabled both SIM cards.
- Find and tap Settings → Network & Internet → Advanced → Dual SIM → Dual SIM reachability.
- Drag the slider beside Dual SIM reachability to the right. The phone numbers of the two inserted SIM cards are entered automatically. If the numbers are not added, you can enter them manually. Alternatively, follow the on-screen instructions.