Personally, I have found that my one chavrusa that is on Whatsapp call is actually quite refreshing. I don’t know what it is, it could be purely the fact that it is simply not zoom and I don’t have to find that link and see that zoom logo again for the 20th time that day. So I like the Whatsapp call all of a sudden. And if you do that, you should make a big deal to the chavrusa that “THIS is your WHATSAPP Chavrusa, and appreciate that!”