When attempting to make a call on an iPhone with an eSIM, users may encounter an error that states "last line no longer available." So, what does this all mean, and what can be done about it?
What Does "Last Line No Longer Available" Mean?
On an iPhone with dual-SIM functionality, this error appears to affect the preferred line. You may encounter the issue if you have more than one cellular plan linked to your iPhone via a standard SIM and an eSIM.
When attempting to dial out from the "default" SIM using the recent call log under Phone > Recent, the error appears most frequently. You'll see an error message that gives you the option of calling using your "remaining" line. You can call from any number that isn't set as your default by tapping "Call" in the box that appears.
Some Possible Solutions
We were unable to reproduce the error because your iPhone does not support more than one SIM card. This makes testing potential fixes difficult.
That said, there are a variety of potential fixes available, the majority of which are anecdotal, with stories of "this worked for me" attached. So your mileage may vary, but if you see this error frequently, you'll most likely have plenty of opportunities to test out these solutions.
The first is self-explanatory: make sure you're running the most recent version of iOS. Errors like this are frequently associated with bugs, so updating your iPhone via Settings > General > Software Update will eliminate a potentially large variable. You can also attempt to update your available carrier settings by going to Settings > General > About and selecting "Update" when prompted.
Another common and simple solution is to enable Airplane mode in Control Center and restart your iPhone. Both of these will cause your network connection to be reset, which may resolve the problem. You can also experiment with switching between SIM cards before dialing in the Settings > Mobile/Cellular Data menu by tapping "Turn On This Line" next to the plan you want to use.
A similar solution is to remove and reinstall your SIM card. On an iPhone, you can do this with a SIM tool or any thin pointy object, such as a paperclip.
Some users reported that enabling (or disabling, then re-enabling) Wi-Fi calling resolved the problem. To do so, navigate to Settings > Mobile/Cellular Data and toggle the Wi-Fi Calling setting. Others have reported success after clearing their recent call log under Phone > Recents by tapping Edit, Clear, then "Clear All Recents" in the pop-up that appears.
Finally, if you're still having trouble, you can reset your iPhone's network settings by going to Settings > General > Transfer or Reset iPhone and tapping "Reset" followed by "Reset Network Settings." All cellular settings, VPN and APN settings, and Wi-Fi credentials will be reset to factory defaults.