What does 'Last Line No Longer Available' mean on iPhone?

The short answer

“Last Line No Longer Available” means your iPhone tried to make a call using a phone line (SIM) that is currently inactive or unavailable. This almost always happens on iPhones set up with two lines (dual SIM or eSIM).

Why does this happen?

This error shows up when your iPhone remembers which line you last used to call a contact, but that line is no longer working. Common causes:

You switched SIM cards or carriers — your old line is gone but your iPhone still tries to use it
Your eSIM was deactivated or removed — the line it’s linked to no longer exists on your phone
A temporary cellular glitch — your second line briefly lost its connection
iOS bug after an update — some iOS versions have had known issues with dual SIM line selection
Airplane mode was recently toggled — one of your lines may not have reconnected properly

How to fix it

Tap the alert and choose your available line — when the popup appears, select the working line to complete your call
Set a default line — go to Settings > Cellular and set your preferred default voice line so your iPhone stops picking the wrong one
Toggle Airplane mode — turn it on, wait 10 seconds, then turn it off to reset both connections
Restart your iPhone — a simple restart often clears the glitch
Update iOS — go to Settings > General > Software Update to install any patches that address dual SIM bugs
Reset network settings — go to Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings as a last resort

When should you worry?

This error is almost always harmless and easy to fix. But keep an eye out if:

It happens on every call — your SIM or eSIM may be deactivated; contact your carrier
You only have one line — this could signal a SIM card or hardware issue worth getting checked at an Apple Store
It started right after switching carriers — your old eSIM profile may need to be manually removed in Settings > Cellular