How to Set Default SIM for Calls and Data on Any Phone By Chester Takau · August 2026 On Android, go to Settings → SIMs (called SIM manager on Samsung) and tap "Calls," "Text messages," and "Mobile data" separately, choosing a different SIM for each if you want. On iPhone, go to Settings → Cellular, set your Default Voice Line, then scroll down and set a separate Cellular Data line. Both platforms let you run calls on one SIM and data on the other at the same time — you set the two independently, not as one combined choice. The short version Android: Settings → SIMs/SIM manager → tap Calls, Text messages, and Mobile data one at a time iPhone: Settings → Cellular → Default Voice Line, then set Cellular Data separately underneath Most dual-SIM phones run one active radio at a time (DSDS) — that's why data can pause on the other SIM during a call unless you turn on the data-during-calls toggle If your default keeps res...