Many phones in Pakistan take two SIM cards, or one SIM and one eSIM. Setting them up once saves you from calling on the wrong line or running out of data on the line you did not mean to use.

Android

1. Open Settings, then look for SIMs or SIM cards (on some phones it is under Connections).
2. Choose each SIM and give it a name, such as Work or Personal.
3. Set the default calls, messages and mobile data lines. Check that data is on the line you want.

Some phones let you pick the line for each call, and show the SIM name on the call screen. Use that if you switch between lines often.

iPhone

1. Open Settings, then Mobile Service or Cellular.
2. Choose each line and give it a label.
3. Set Default Voice Line and Cellular Data, and turn on Allow Cellular Data Switching only if you want the phone to change lines by itself.

What to check

• Read the data balance on each line after the first day. A line that is not your data line often shows zero usage, and that is normal.
• Check that the second line can receive calls and texts. Ask someone to call it once.
• Keep your IMEI numbers noted: a dual SIM phone has one per slot.

Common mistakes

• Setting the data line to the wrong SIM, so you use up the balance you meant to save.
• Forgetting that the second line may need its own WhatsApp or banking setup. Check WhatsApp on two phones with the same number before you sign up.
• Assuming that an eSIM and a physical SIM work the same. See what an eSIM is and whether your phone supports it.