Originally Posted by haopei
I should mention that I was the Big Blind at the time.
So, is that all clear for you? I mean, I'm no expert, but we were all raw beginners at some time.
The only time this happens is 1) you are the big blind, 2) it is in the preflop betting stage, 3) someone called your big blind, 4) no one raised.
At this point there is no bet for you, as the big blind, to call because you put in your money before the cards were delt, so you cannot call your own bet. Someone else called your big blind bet, but, as the big blind before the flop, you have the option to still raise their calls.
As Mr.Bove says, if someone raised, then you would have the option to call their raise.