Someone calls you on your com radio, and you dont know who it is:
Radio:"Hello? Testing, testing!"
You:"Hello, Who are you?" (U are a bit worried but also thrilled to hear someone new´s voice)
Gives this response:"I'm David, I just started working here."
You:"Why do you have Saras radio?" (U are a bit worried but also thrilled to hear someone new´s voice)

Your friend David calls you on your com radio:
David:I just read someone's journal.
You:"David! How can you? That stuff can be very personal!" (Pretending to be offended, like ther person has done something forbidden)
D:I know! I'm sorry! I didn't know it was a journal when I picked it up.
V:"I am messing with you! Did it say anything exciting?" (Funny, your joke worked.)
D:Sadly no. Just depressing stuff, don't want to be here, miss his family and so on.
V:Oh, yeah going away to work on a desolate space station for a couple of years isn't for everyone.(Serious.)

Your friend David calls you on your com radio. Flirty/Friendly

David:This guy brought his weight training gear and he is lifting some heavy weights.
You:Is it too heavy for you?

D2:Nono, this is nothing compared to what I lift.
You:Yeah, sure Arnold. So you are not a big guy then?