Is it appropriate to phone a researcher/academic? (Germany) I am applying to do a master's thesis at a German research institute. The institute's website encourages applicants to contact the researchers directly (and does not give more information about the application process). I have been wondering whether initiating this contact over phone could be a way to make a strong first impression, and would make it less likely that my subsequent application mail will disappear in their inbox. The goal of the phone call would be to ask whether their group has an open spot for a master's student etc. On the other hand, I am worried I would be breaking some social code by making such direct contact with someone 'higher up in the hierarchy', or that they would think I am wasting their time by calling in person. 

So, my question is: Would it be appropriate to phone a researcher/academic with such inquiries?

I realize this will depend on the person being called, but I think it is still possible to answer whether this is generally acceptable within cultural norms. 

Note: Many, but not all, of the researchers list a phone number on the institute's homepage.
I don't appreciate being called; it imposes your time schedule on me. Others differ. However, I suspect that email is your safest bet.

The practical problem is that many universities in Germany have been closed due to COVID-19, and the numbers listed will be the work numbers. Either you are calling an empty office, or your call is forwarded to the persons home adress, which may not be what you want.

@MassimoOrtolano makes a good point in emphasizing the unannounced part of a phone call. You could sent an email to make an appointment. I would be fine with that.