I got my new iPhone yesterday and had some issues with the Apple transfer only moving the 2 esims from my "Old" 15 Pro Max to the new, 16 PM. The Roamless acount and esim did not attempt to swap, so I contacted them via Chat in their app. They responded in just a few minutes and were very eager to work on the issue. We got the esim installed easily, but my account credits did not post to the new phone account. I finally gave up after about 2 hours of Chat and got some sleep. They were able to set up the account overnight and I am very happy with their perseverance without my input to correct the issue. This morning, I had the full balance and service in place.

So, just a shoutout to Roamless Customer Support for very helpful, prompt attention for an issue. Their rates are a mixed bag since they are far from the cheapest, but do have "Forever" data after purchase and with the current promo it sorts out at $1.96/Gb for US and most Euro service. The promo provides $25 credit for a $20 purchase. I bought it on a whim since I use T-Mobile as my primary carrier in the US and abroad. I also have a US Mobile esim for voice service while roaming, and that esim did not switch to the new phone automatically either. A quick chat with them was all that was needed.

WhatsApp, IOS messages with local esim
 

I have a UK phone and number associated with WhatsApp and IOS Messages. I will be purchasing a local esim for the USA for 2 weeks. I want to use WhatsApp and Messages on the local sim so that my existing contacts can message me without needing to change to my new temporary local number.

Is this possible? If so, do I have to change settings once the esim is installed and activated?

your scenario is possible. No need for a setting change. Just deny the number change pop up from WhatsApp.

That's true for Whatsapp, but not for the stock Messages app.

If you've switched off your UK SIM, your phone won't let you send and receive iMessages with that number, and it's not possible to send or receive SMS to a SIM that's off.

If you can get by with only Whatsapp, you're good, but if you need to SMS or iMessage people, you'll have to leave your UK SIM active. iMessages will go over your American SIM's data and be free, but any SMS you send or receive would be chargeable unless you're able to set up IMS ("wifi calling" over the other SIM's data, effectively) but not all carriers support it.

So if I turn off my UK sim and use the local esim will iMessage people be able to message me? I only need to stay in contact with iMessage and WhatsApp people, not SMS people. If I have to leave my UK sim on then it defeats my purpose of the travel esim. Thanks

No iMessage isn’t going to work if you switch off your UK sim. Why does it defeats your purpose of the travel esim? Just switch off data roaming?!

My hope was I could turn off the UK sim to avoid charges and turn on the esim for data and still use WhatsApp and iMessage normally. It sounds like isn't possible.

I believe there is a grace period between which iMessage is still available on a previously-utilised SIM: it should be ~30 days, though do google it to confirm…

I use my domestic sim set to WiFi only which uses the data of the local sim to check iMessages without any roaming charges. The UK provider has to support WiFi calling with no geo restrictions for your destination.

This feature is often called IMS and has been discussed in this thread and a couple of other threads.

Depending upon what model phone you have you may be able to accomplish your goal fairly simply. I am assuming you have a dual sim phone however.

If so, and you have WiFi calling on your UK voice line, you can keep it active but assigned to a non roaming carrier partner in the US. For iPhones, this is under: Cellular-UK Line-Network Selection-Automatic to Off, then chose a carrier you cannot roam on with your UK carrier. Android has something similar. Once your UK line cannot connect, it should default to "Using Cellular Service" of the roaming data sim. At this point, the data sim is behaving like a WiFi network for your UK WiFi calling. This also assumes you have free or discounted WiFi calling on your daily voice line.

I have US service and this system has been available for several years on iPhones and some Android models. It's called IMS for Apple products and something like Standby Calling for Android. Once set up, it's rock solid for function and awesome for travel. You can test it prior to departing for configuration and function with any two available lines. There are several discussions on Flyertalk over the past few years if you care to investigate further.

Would it matter if the sender used an email address rather than a phone number to send the iMessage? I'm fully ignorant, but it seems like an incoming iMessage to an email address should work on any line.

iMessage does allow you to select your email as an active address. I keep mine unchecked because I have 2 lines already in use for that. I travel with T-Mobile lines for data and voice service with the IMS setup. I also use a US Mobile Verizon based esim for local calling while overseas, but that's another story.

Edited to add: BTW, the major US carriers all allow email forwarding to Text Messages via a combination of your phone number in an email combination. They appear somewhat like, [email protected], depending upon the US carrier. Is this available or common on UK carriers?

Do you need your iMessages immediately? I turn my Primary on and my secondary off once a day, when I am connected to Wi-Fi. Data roaming off. This allows messages to download. You could do this several times a day, download messages in batches. If anyone needs to contact you urgently they can do it through WhatsApp. It works fine for me, I understand it wouldn’t work for everyone. I haven’t had much luck keeping the Primary on, Wi-Fi enabled, data roaming off when I am using my eSIM. It seems OK for a few minutes but then the signal declines to zero over a few minutes. So I only keep one open at a time, either the Sim or the eSIM.

If your phone is dual SIM turn off roaming on your UK SIM and leave it in the phone or better yet lock your phone to your UK carrier on the plane with the manual network selection mode. You might even get WiFi calling over backup cellular that way and get your green texts for free.

My phone is dual sim. If I leave the UK sim on but turn off data roaming and do not use this sim to make calls or green texts, I will only use the esim for data. If I do this I won't be charged at all, correct?