Even though they said they'd get back to you by a certain day, it's pretty common for those days to come and go. I used to be a recruiter and it was quite common for hiring managers to take longer than they said they would (even though they'd be breathing down my neck to hire someone).
That said, the HR person should at least have returned your phone call and email by now. From the recruiter's point of view, you shouldn't call or email anymore. No matter how eager and excited you are, I would (as a recruiter), find it annoying to keep hearing from the same person. She should reply, but if not, it's probably a sign that the company is not as well run as it should be and there would be a lot of frustration if you ended up working there.
I'd start looking for something else, and keep an open mind. I know you're excited about this one, but I think you should move on. I'm sorry.