Is it appropriate to use professors’s phone numbers?

Question

11 days ago I wrote an email to a professor of a famous university in the US to ask about potential open positions in their laboratory to carry out my Master’s Thesis. He responded immediately, CC’ing the group administrator to figure out the mechanism to make the thing work out. He also suggested that we had to have a chat in about a week. After 5 days (last Friday) I tried to contact the professor again to schedule the meeting but he didn’t answer my email. I waited until Tuesday in the afternoon to send another email specifying that I have a deadline to apply for my scholarship (which is essential because I would not be paid) and that I need to schedule the meeting as soon as possible, according to their preferences. He didn’t answer for the second time, so after 2 days I directly contacted the group administrator, who just forwarded my email to the professor. I’m now waiting for an answer but I feel like the emails are just getting lost among the many others he receives.

In the very first (and only) email I received from them, they included their office and mobile phone number, in the contact information section under their signature.

I was wondering if it would be inappropriate to send a message or try to call them on their mobile phone number, because I live in Europe and it is totally impossible for me to reach out to them if not by email or by phone.

Answer 1

This is more or less re-writing hm1912's comment as an answer, but if the professor included the phone number in the email, it should be appropriate to call, especially since repeated attempts to contact by email have not reached him.

It might be a good idea to call the office phone number first (during working hours in his local time) and then try his mobile number later if that does not work. Good luck!