I use a phone plan that doesn't work outside of the US. It's perfectly fine for me while I'm inside the US, because it's a cheap plan (yet still very expensive by my standards), and I don't need anything more.
However, things get complicated when I travel - I go and spend several weeks in Europe almost every year. What I usually do is that I get a local SIM card with a limited plan, to be able to message people in the countries I visit with a different plan than my US plan which wouldn't let me do so anyways.
It usually gives me a lot of grief doing so, because not only of Two-Step Verification issues with some accounts like Facebook or Gmail, which rely heavily on a phone number I cannot access anymore the moment I land abroad, but also because WhatsApp links your account to your phone number to function properly, as opposed to other services that rely on your email address.
People have complained that when I was abroad, they were getting messages on WhatsApp from a different account than the one they're used to - even though both of them were me. And when I came back to the US and reverted my WhatsApp number to my primary US phone number, and the foreign phone number I was using got cancelled by the phone company, they've complained that their messages sent to the secondary account never got to me.
I understand that my situation is rare - but I don't think it's unique (my phone plan provider has 10 million subscribers and none of their plans allow you to call or message outside the American continent). It's extremely frustrating to have to spend countless hours on devices having to prove my identity, or not being able to, and it has made travelling with digital devices a real pain.
I would like to change the primary international messaging service that I use to an app that relies on my email and a secure, encrypted password, rather than one that bases my identity on my phone number.
It needs to be secure, accessible over wifi, able to run on most of my contacts' phones and computers, and ideally has video call capabilities.
Is there such a messaging service?