Sci Fi Short Stories (I need h-e-l-p)

[smearbrick1]

When I was younger, I remember reading a book filled with Sci Fi short stories. The one story focused on a man attempting to make a phone call from a phone booth. When he made the call, he accidently called an alien ship or something that was attempting to take over earth (I can't remember all of it). Ultimately, he gets captured, gets sent back, but ends up in some sort of time loop where he's doomed to make the same call over and over again.

One other story has to do with an alien/human exchange program where humans are exchanged for aliens and the humans are put through a series of technology tests by the aliens to test out knowledge. Ultimately, the aliens have the humans build a perpetual motion device and refuse to let the humans leave...

I can't remember the finer details of these stories, and these are only two of a bunch of stories included in the collection I read.

Does anyone know what the name of the collection is?

[smearbrick1]

Bump

[Faustus]

All new to me. Sorry.

[offline]

Same here. Maybe try one of the SF newsgroups.