If I get a local number via Mobal while I’m in Japan, I assume that anyone I want to stay in touch with via WhatsApp (i.e., my friends in the US), that I must give them my Japanese Mobal #, yes?

This may be a dumb question but…. I am going to get a voice/text/data plan thru Mobal, so that I can have a local Japanese number to communicate with friends in Japan (some of whom don't use WhatsApp or any other apps)..

So if I have a new eSIM for my phone, I guess that means that the US number associated with my phone will be temporarily deactivated. And I guess (to save money) I should call my local US phone provider and tell them to 'cancel' my phone coverage…..put my account on hold(?) for the three months I'll be in Japan?

And then when it comes to friends in the US that I'd like to stay in touch with (say via WhatsApp), do I have to tell them what my new/temporary Japan phone number is? I assume during the time I have an eSIM that gives me a Japanese number, that they only way they can connect with me via WhatsApp is if they have my Japanese #, right? If they tried to connect with me on WhatsApp using my US #, it wouldn't work?

OR is it that, my phone will recognize that my US # has changed over to a Japanese numbers, and so anyone trying to connect with me on WhatsApp using my US #, will automatically be connected to me via my Japanese number?

Thanks all.