Got phone number, but always voicemail.

There is a girl that I knew back in High School that I knew of but not really well, she graduated a couple of years after me. She had a sort of part time job while she was in school working at a nearby hospital with my mother, who helped train her on the job, so I sort of got to know her a little more because of that. I get to see her it seems every once in a blue moon as we do not live all that close to each other, in different cities. So I decided to try out the Myspace thing, to see if I could find her on there as well as a find a few friends. So we became Myspace friends and talk to each other that way and such through messaging and comments and such. She told me a few times shed wanted to hang out while she was in town and such, but that never worked out because the couple of times shes been around I wasnt able to hang out with her. So I message her saying that I would really like to meet and hang out as she had suggested a few times. She responds by saying yes we should definitely hang out and she gives me her phone number and tells me to call her. Now I wasnt sure exactly what to do, so I waited a few days to call her, and when I did, I ended up getting her voice mail, so naturally I left a message. I called a couple of days later and once again got her voice mail, a few days later same thing, as well as every time since. Now I dont call repeatedly I usually call once every few days, most of the time I will leave a message because I always get the voice mail, I dont know if I should call more or what, I just dont want to be a nuisance to her by calling too much. So is there a potential reason to me never being able to get in touch? Sorry if this was too long winded, this is just something thats been on my mind for the past little while, any advice you guys could provide I would greatly appreciate it, thank you in advance :)

Text messaging or e-mail is a lot Easier to communicate than voicemail.
Does she treat you as a potential boyfriend or Does she have one already?
Hospital hours are pretty late, maybe she has just been busy.
These type of situations, are good life experiences that you will take to the next Girl you meet.
Most high school relationships don't last, and are just a way to get comfortable when you hDad to college or university.

P.S. I've been burned myself like this, and don't let it get to your head.
I called to figure out what was making her sad, but got very little as a response each time I called and it just got frustrating enough to move on with my life .
It makes women a lot easier to read when you've been hurt in the past or succeeded.

If her voicemail isn't constantly full, and you can always leave a message, that means she's checking it and getting your messages. If she hasn't responded, she just not interested, but she's too spineless to tell you upfront, in my opinion. She's probably hoping you stop calling. Though, you might just straight up ask her on whatever avenue of communication you do have with her why she doesn't answer her phone, to force an answer.