If your eSIM isn’t properly linked to your IMEI/line, it might work on Wi-Fi (like VoWiFi at home) but suddenly stop working when you leave.
Check whether your iPhone shows one EID (Embedded Identity Document) and two IMEIs (International Mobile Equipment Identity numbers).
- The EID is tied to your device’s eSIM capability—it’s essentially the digital identifier that allows your phone to load and manage multiple eSIM profiles.
- The two IMEIs are there because modern iPhones support dual-SIM functionality (two active lines at the same time).
Even though you can store 8 or more eSIM profiles on a single iPhone (depending on model and carrier support), the limitation comes from the fact that you only have two IMEIs. This means you can only have two eSIMs (or one physical SIM + one eSIM, on models that still support a physical SIM) active at the same time.
So, in short: your phone can hold many eSIMs in memory, but it can’t use more than two active lines simultaneously, because that’s all the hardware (two IMEIs) can handle.
See the pic below

Also, if “Automatic” is turned off in Settings → Cellular → Network Selection, your phone might not connect to AT&T when you’re out and about.
Try these..
- Toggle Cellular & eSIM
- Settings → Cellular → Cellular Plans → Toggle your plan off and on.
- Restart iPhone.
- Reset Network Settings (won’t erase personal data, but clears Wi-Fi/Bluetooth passwords):
- Settings → General → Transfer or Reset iPhone → Reset → Reset Network Settings.