Passive bandpass filter
First, consider that with a passive bandpass filter, everything gets attenuated to some degree.
(With an ideal zero impedance source and infinite impedance load, a passive low-pass does not attenuate DC; a passive high-pass would not attenuate infinite frequency if it existed.)
I calculated the corner frequencies of your two filter stages.  Neither matches the frequencies you mention in the question, and I note that the low-pass frequency as designed is lower than the high-pass frequency.  Check your calculations for component values.
I can't tell what simulation software you're using.  Does it have the capability to create a Bode plot (frequency-domain analyisis)?  That might be more helpful to understanding.