Like the Gemini, the Cosmo should work either way up: there are speakers and mics at both ends, and it uses the orientation sensor to make the upper one the earpiece and the lower one the mic. It should also switch in mid-call if you turn the unit the other way up.
But, at least on the Gemini, it doesn't always work perfectly… Occasionally it seems to pick the wrong orientation, and/or fail to switch when you rotate the unit.
(Don't know if this depends on the OS version and/or model/batch.)
Luckily, it's usually fairly obvious when that happens, and because the device is largely symmetrical it's no problem to turn it the other way up.
