When traveling, it’s helpful to use a temporary local SIM card to increase coverage and reduce cost. Swapping your physical SIM with a new one gives you seamless access to apps that rely on data (e.g. WhatsApp, Messenger) while also giving you 30 days of seamless access to Apple’s services (e.g. iMessages, FaceTime).
The latter is only possible because of how Apple treats a new physical SIM card:
- You get a “iMessage and FaceTime Number” notification “### will continue to be registered for iMessage and FaceTime. You can change this in Messages Settings."
- When you go to the iMessage settings, you see that it has a 30 day counter and says “This number is registered to your Apple ID, but is not associated with this phone. You can keep using the number for iMessage and FaceTime until it expires.”
This is perfect since it means for any trip less than 30 days, you’ll experience zero disruption on Apple's services too while using the local SIM.
As of 2018, rather than using a physical SIM, you can now use an eSIM, and newer phones only allow you to use an eSIM.
When attempting to temporarily disable1 my original SIM and enable the local eSIM, I don't see how to get the same 30-day iMessage grace period.
Is there a way to disable my original SIM, enable a temporary local eSIM, but still use iMessage/FaceTime with my original number (e.g. for 30 days)?
1 I’m disabling the old SIM since it’s the only way to guarantee I don’t accidentally get charged by my carrier if I send/receive a call/text/data on my old number. For example, assume I leave my original SIM on, but set Default Voice Line to the local eSIM. I could still incur charges if someone sends an SMS to my old number, or if I pick up a call sent to my old number.