Like the Gemini, the Cosmo has two combined mic/speakers; sound enters and exits through the rows of small holes on the ends of the unit, and through the two slots on the top near the ends.
When closed, it's intended to be used like any other phone, held roughly vertically. In that position, the uppermost end acts as a speaker, and the lower as a microphone.
When open on a desk, I expect it works like a laptop, with both speakers and both mics in operation.
The Gemini would occasionally get confused about which end is which, especially if you turn it while taking a call; it's possible that the Cosmo gets similarly confused, perhaps more easily in this early version.
As a workaround, try turning the unit different ways. In particular, if it's closed, and you can't hear or be heard, try holding it the other way up. And if possible, try not to switch between open and closed in the middle of a call.
