Academic dean (interim graduate program director) not responding to e-mails
Depending on the size of the institution, the dean herself may answer none of her correspondence directly no matter whether by email or formal letter. Deans usually have office staff to filter all communication and sort it by priority. Deans spend an inordinate amount of time in meetings at all levels, both on and off campus. If you sent an email to a vice president of some relatively large company you would get the same result. Multiplying your attempts only makes the problem of scale worse. Your repeated attempts are received as just noise. 

A dean at a large place may not even be able to field email from faculty directly, much less from students. You can enquire from the office of the dean what is the best way to obtain answers and to meet your needs, but don't expect that personal contact is likely or even possible. 

You can complain, of course, but it would probably need to be to the dean or to one of her superiors. But they have the same sort of office procedures. 

In general, however, I'd suggest that you direct questions to the lowest office in the organization for which it makes sense. Usually that is the department office, perhaps even a secretary there. But perhaps even an individual faculty member is more appropriate unless your issues are about misconduct at some lower level that really requires upper-level action. 

I went to a college with about 2000 students and never corresponded with the dean. I went to a graduate institution with 40,000 students and never even knew who the dean was.