I've been using VIPole for about a week. They claim end to end encryption...among many other privacy features. They support phone calls but i have no experience using it. The general beef r/privacytoolsIO and r/privacy have...and rightly so...is the program is closed-source. Vsee has been working well for video calls.
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I added the PP link just for general interest. I would have to rely on the expertise of others regarding source code as I would not know how to read it. Although I'm not a paid subscriber, those who are were supposedly (eventually) able to use their own encryption plug-ins.
It's difficult to find a decent amount of independent information on this company.