Unfortunately, these are all the same group of scammers. They say they are the IRS, Academic Advisors, blah, blah, blah and they are all non native speaking so most probably from Pakistan & India. When I used a job search engine, my info was spread so in the last week I've gotten at least 50 calls. Sucks to be them that I don't answer calls from #s I don't know. If legit, the'll leave a voicemail. It's the Nigerian email scam in cell phone form.
If you need to leave a phone number, but don't expect to need a call from the site, just use one on these harassment numbers. that way they will be busy calling each other.