Does anyone use WhatsApp/Viber when on their travels instead of roaming?

I use What�s App to communicate with local establishments and people when traveling internationally.

Avoiding international roaming while using your domestic number has become easier in recent year with the iPhone, Pixel and S23. There are several threads discussing iPhone IMS with mentions of Pixel backup calling and the Samsung S23 which are all capable of making WiFi calls using a local esim.

I simply buy a local SIM card and then use it with my phone. My phone has 2 SIM cards and to me it is more handy and having an e sim. Just local 5g data charges only and extremely cheap in Asia. Certainly not worth the roaming charge.

Which phone are you using? I make and receive calls using my domestic sim with no international roaming by using the data of a local sim. My iPhone when traveling is configured for the domestic sim to make WiFi calls using the local sim. I use WhatsApp for local communication for international travel

I use a two physical sim iPhone 14pro. Buy a local sim and put it in one slot and use that sim for data. Yes my local calls won't be received but I hardly use my local number on normal phone calls anyway.

My local calls and texts are received after configuring IMS which the IPhone XR and newer supports. Configuring IMS with a local international sim avoids international roaming charges. The OP is missing IMS as a valid option for communicating back home with international travel.

I am sorry I do not understand. I do not incur international roaming charges as I use WhatsApp or Viber and a couple of others to talk or text when traveling. The foreign SIM with the data is extremely cheap and lots cheaper than I pay at home for my mobile phone charges. Does IMS work only between iPhones or any phones?

IMS works the same as if the phone is physically in the home country by using WiFi over the cellular data of the 2nd sim. You can call and text any domestic number with no roaming charges when traveling internationally.

Several threads in this forum discussing IMS. A few Androids support similar functionality. You configure the domestic sim not to roam and WiFi calling has to be enabled. Prior to IMS I would use WhataApp or Google Voice to communicate with my family when traveling. I only use WhatsApp for overseas contacts.

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if you want your chat or voice to be spied by Facebook and end up having it on a NSA server in Utah, use WhatsApp.

I use Signal that was created by the same guy that created WhatsApp. Needless to say I stay away from anything owned by Facebook. This weekend I was talking with wife on triming grave vines. A few hours later she was seeing Facebook ads on services to trim grape Vines.

I am currently in Asia and experimenting with a US Mobile Shared “Warp 5G” plan on the Verizon network. Used as the voice line with an IMS setup, it provides free voice calls to over 180 countries around the world while roaming. I have T-Mobile as my roaming data service which gives me 5Gb per month of free high speed roaming data. This combination works very well and setup is easy. Using IMS, any data service should work, so a local sim or Airalo, etc. should be fine as the data side of the IMS function. Among other features, it eliminates the need to hunt for a voice line non roaming carrier at every location for IMS. The US Mobile line can never get service, so it always reverts to “Using Cellular Data”.

I’ll be home in a week and intend to post my experience with this system here on FT. The US Mobile plan costs $10 a month inc. taxes & fees. It gives a voice line, and 2Gb of Verizon priority data per month while in the USA. This configuration is probably going to be my travel communication setup going forward.

Can you explain what do you mean by "IMS" and specifically "configure IMS", pls?

iPhone term is IMS, Google Pixel term is backup calling, Samsung S23 term is DSDV. The objective is to use your domestic sim over WiFi using the data of the 2nd local sim without international roaming charges. All 3 phones achieve the same result with different steps. At one time I travelled with 2 phones. One had a local sim with hotspot enabled and my other phone connecting using WiFi. Now some phones are capable of doing the same by adding a 2nd sim and changing some settings. My son in Europe called the US using his domestic number without incurring any charges other than his local data sim.

The iphone has to be unlocked, XR or newer, WiFi calling has to be enabled and the domestic sim is set to a non roaming partner or has data disabled. The sim is always active similar to airplane mode. Disabling the SIM interferes with calls and texting.


The iPhone domestic sim will use the data of the local sim with no international roaming charges. draver has been journaling his IMS travels using US Mobile and T Mobile international data. There is a Verizon plan which doesn�t work IMS. Some Australia/New Zealand providers have geo location restrictions for WiFi usage. Many US MVNO�s without international roaming work using IMS or one of the other options.


Hopefully others will add their comments since multiple users can take advantage of this feature when traveling internationally. I have a work Google Pixel and can see the backup calling switch but I have not added a sim to test the functionality.

Thanks a lof for this detailed explanation, much appreciated.
i got confused when I saw IMS, as IMS is a part of the cellular/mobile network.
i will have to find out more about this feature, it looks interesting.

Your are welcome 👍. I was waiting at the doctor and typed the reply on my iPhone. You can try this setup with 2 domestic sims before you travel abroad to test with a chance to ask any questions. I probably first heard about this setup from a Delta flight attendant. Her normal work route is London with a layover before her return.