Is it a good idea for an applicant to a graduate program to call a potential supervisor, if he does not answer emails?
Do not phone.  You should not have emailed.  There is a standard process for acceptance into graduate programs, and contacting the professor is not part of it.

In the US, at least, and in the fields I'm familiar with, professors with any kind of international profile are inundated with applications to work in their lab/graduate program, even though in most cases, the professor has little or no control over whether students are accepted into the graduate program, since that is run by a graduate committee.  Accordingly, emails to a professor asking to be taken as a member of their lab, before the student is accepted into the graduate program, are worse than useless; they are pestering a busy person with irrelevant requests.  Such emails are typically deleted as soon as the professor reads the first sentence, or at best -- if the professor is extremely generous -- forwarded to the appropriate person. 

This is multiplied by ten if the email sender doesn't have a good grasp of English, because (fairly or not) such emails are often perceived as simply carpet-bombing, spammed to scores of people on the off-chance of a hit. Again, professors may receive dozens of such poorly-written begging letters per week, almost all from completely unqualified candidates. (The question here, while far better written than many such letters, is far enough from standard English that it would likely hit this barrier.)    

It is multiplied by a thousand for a phone call.  It's quite likely that if you did make phone contact with the professor, the act of phoning would add you to the "Do not touch this person with a ten-foot pole" list, even if you were accepted to the graduate program. 

If you are interested in working with this person, there is probably little point in contacting her directly. Go through the standard graduate student application procedure and then once you're accepted, contact the person and make it clear that you are already in the program.  

The exception would be a potential graduate student who is truly exceptional.  This does not mean an overlap of interests; it means an overlap of interests plus a very strong skill set, meaning pretty significant work in the field already, or some other really out of the ordinary ability -- not grades, not a prestigious university, but actual demonstrated skills.  And this would not, typically, be communicated by the prospective student, but by someone associated with the student whose judgement would be more reliable, like a professor or industry expert.  So even in this case, the student should not be pestering the professor with emails or phone calls.  

There may be individual exceptions, who welcome this sort of thing, but the odds are very much against you.