"Because. This is Pam" - I thought they were talking about their friend Pamela :D
Is this the sort of dismissive "Because" used when a parent or child doesn't want his/her reasons to be questioned? Or is it a pensive "Because ... and here is the answer"? Or does it just depend on tone, like in English? Thank you.
Yes, like English, it depends on the tone. It could convey a range of meanings.