# iOS - Dual-Sim with SCA
**Third-party apps like the SCA can’t actively control which SIM card is used for outgoing calls.** \
\
SCA tells the operating system to dial a number. \
iOS then decides which SIM to use based on device settings\
—in this case it would be the default line for outgoing calls.\
\
Usually, the business SIM is set as the default.
**The only way to influence this is:**
* When creating a private contact, manually set the preferred SIM.
* Or, during the first call to a new contact, choose the desired SIM (e.g. “Private”) in the pop-up.
The iOS typically remembers this choice and uses it for future calls to that contact.
**We recommend, the following:**
* The business SIM should be set as the default for outgoing calls in device settings.
* All private contacts should be saved with the private SIM assigned for outgoing calls.\
**How to set Default Voice Line:**
* Go to *Settings*
* Go to *Mobile Service*
* You can set your *Default Voice Line* to Business or Primary.
Underneath, both SIM lines (Primary and Business) are visible with their numbers.\
This setting defines which SIM line will be used first by default when you dial a number.\
**How to assign Prefered Line for Contacts:**
* Open the contact you want to change Preferred line.
* Tap the area between the profile picture and the name to edit the line setting.
* You can set the ***Preferred Line*** to **Last Used**, or choose to always use **Business** or **Primary**.
