When to follow up?

I sent my resume for an internship program. The lady sent me an email back to set an appointment for an interview, I replied but I never got a response back. I sent her follow up email. She did not respond. I called the clinic again and they told me they will call me back. I did not hear from since then. Should I call them, email them again? I feel like I have been very intrusive about it, but I really want that internship position!!!! Please help! Thanks! Sent from my iPhone using... When to follow up?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums