Receive USA calls while in France and Switzerland on a mobile?

Who is her carrier? Check that out first. Why not just add international service to her phone for the time you are there. That way it is still a local call for whoever is calling her. This is the easiest way by far.

You could forward her US phone to a French phone you purchase while there but then any help you might need with the French phone will be in French - how's your French? And you would need to be able to forward her phone AFTER you land in France and obtain the French #

OR

Get the Skype # and forward her phone to it before you leave US then add Skype to French phone.

For skype you will need a wifi connection - some places with free wifi block skype ports as it really uses bandwidth so that may not always work.

Do you really want to spend your valuable vacation time chasing technology? See the first suggestion.

Christi is right - it's simplest to just bring her phone. If, by chance, she uses TMobile, calls are 20 cents per minute. Texts and data are unlimited and free. Calls made over wi-fi (like in your hotel) are free also. It's a great service. I've done the forward-the-number to a Skype number thing - it was a pain, call quality was not good. Once TMobile debuted their great plan, I never looked back.

Another T-Mobile fan. Husband had to take a number of business calls. Also made calls using the Internet & it was very clear.

Att passport calls are $1 min., unlimited texting on $30 plan

Pierre,

Could you clarify whether your Mom's "regular USA number" is a cell phone or landline? Does your Mom own a cell phone and if so, which network is she with.

With more information, it would be easier to offer more specific suggestions.

Yes, I was just on the Germany, Austria, Switzerland trip with Project Fi. It was like I never left the country technology wise. The other huge bonus with Fi, which I did not do, is that you can get data only SIMs (for free) for other devices (tables, phones, etc). Instead I activated the wifi hotspot on my own phone for my wife's phone to use as she does not have international support. Data sims are only officially supported on a subset of devices, so order and test before traveling.

Another plus I noticed on Project Fi is that while you can use the +(country code) (number) style of dialing, you can also use the local format of the country you are in. If you see a phone number listed somewhere, you just dial it as is without figuring out which part you drop before adding the country code, etc.

Hotel WiFi is still important for things like overnight photo backup as the Fi datarate is only around 300kB/s and it does charge $10/GB. Oh, and don't forget to set do-not-disturb mode at night, otherwise you'll get calls at 3 am asking if you want solar power for your house, etc.

Just remember that Project Fi is available on only a very limited number of specific phones. It is in no way as universal as normal GSM service.

OK, so what's the catch?
The biggest downside for you is that Project Fi is available only on LG's Nexus 5X, Motorola's Nexus 6 and Huawei's Nexus 6P. This means you'd have to buy a new phone and leave the Apple iPhone ecosystem if you wanted to switch to Project Fi.

I have Verizon, and just added international to my Galaxy S7. If you use non-wifi data, it's $10/day, and the allowance for data, calls, texts comes out of your regular plan. It was super easy and I set it up online.

Just finished six weeks overseas. Had to make numerous calls to the States during that time and never turned off my data. My Project Fi phone cost me $12 over my $30 normal monthly rate for the whole time overseas. Thanks Kaeleku for writing about Project Fi a few months ago.