Use this guide right after you land. It ensures your travel eSIM provides data, while your primary line behaves the way you want (on or off). The most important steps are selecting the Cellular Data line and setting Data Roaming correctly.

TL;DR checklist

• Cellular Data → set to your travel eSIM
• Data Roaming (travel eSIM) → ON
• Data Roaming (primary SIM) → OFF
• Allow Cellular Data Switching → usually OFF (prevents accidental fallback)
• Decide if you want your primary line ON or OFF (see “Choose your scenario”)

Step‑by‑step

1) Select the travel eSIM for data

1. Open Settings → Cellular (aka Mobile Data).
2. Tap Cellular Data → select your travel eSIM.
3. Tip: Rename it first (e.g., “Jordan eSIM”) via Cellular Plan Label so it’s easy to recognize.

2) Turn ON Data Roaming for the travel eSIM

1. In Settings → Cellular, tap your travel eSIM.
2. Tap Cellular Data Options → Data Roaming → ON.

3) Turn OFF Data Roaming for your primary SIM

1. In Settings → Cellular, tap your primary plan.
2. Tap Cellular Data Options → Data Roaming → OFF.
3. This prevents accidental data use (and charges) on your home line.

4) Control “Allow Cellular Data Switching”

• Go to Settings → Cellular → Cellular Data.
• Turn OFF Allow Cellular Data Switching to keep iPhone strictly on the travel eSIM for data.
• Only turn it ON if you’re comfortable with iPhone automatically switching data lines.

Choose your scenario (Primary line ON vs OFF)

Scenario A — Keep your primary line ON (most common)

• Pros: You can still get calls/SMS/2FA on your main number. iMessage/FaceTime stay tied to your number.
• Cons: Your carrier may charge for incoming calls/SMS abroad (even spam).
• Settings recap: Cellular Data → travel eSIM; Data Roaming (travel) → ON; Data Roaming (primary) → OFF; Allow Cellular Data Switching → OFF (recommended); Optional: Default Voice Line → Primary

Scenario B — Turn your primary line OFF (avoid all voice/SMS charges)

• Pros: Blocks incoming calls/SMS on your main number → avoids per‑message/voice charges.
• Cons: You won’t receive SMS/voice. iMessage/FaceTime may switch to your Apple ID email until you re‑enable the line.
• How: Settings → Cellular → [Primary] → Turn On This Line → OFF.
• If iMessage/FaceTime switches to email: Settings → Messages → Send & Receive → reselect your phone number; Settings → FaceTime → ensure your number is selected once the line is re‑enabled.

Optional settings (use as needed)

• Default Voice Line: Settings → Cellular → Default Voice Line → choose Primary (or your local eSIM if you have a local voice number).
• Wi‑Fi Calling: If supported by your carrier, enable Settings → Cellular → [Primary] → Wi‑Fi Calling to place/receive calls over Wi‑Fi.

Test your connection

• Open a webpage or maps app to confirm data is working on the travel eSIM.
• If data fails: re‑check the four key toggles at the top of this guide.

Common pitfalls (quick fixes)

• Chose the wrong Cellular Data line → set it to the travel eSIM.
• Forgot to enable Data Roaming on the travel eSIM.
• Left Data Roaming ON for the primary SIM → turn it OFF.
• Allow Cellular Data Switching ON → turn OFF to prevent fallback.
• Turned primary line OFF and iMessage/FaceTime switched to email → re‑enable the line and reselect your number in Send & Receive.

When you head home

• Cellular Data → switch back to Primary.
• Data Roaming (travel eSIM) → OFF.
• Optionally turn off the travel eSIM line or remove plan.