B733 CREW MISINTERPED CLRNC AND OVERSHOT ASSIGNED ALT.

Narrative

ON THE QBALL ARR INTO STL; WE WERE HANDED OFF TO APCH AND GIVEN HDG 050 DEGS. ON THAT HDG A FEW MOMENTS; WE WERE CLRED DOWN TO 7000 FT AND READ BACK 7000 FT WITH NO COMMENT FROM THE CTLR. I COMMENTED THAT I WAS HAVING DIFFICULTY UNDERSTANDING THE CTLR. A FEW MOMENTS LATER; APCH CTL CALLED OUT TFC AT 11 O'CLOCK POS AND 15 MI AT 7000 FT HDG SEBOUND. WE WERE GIVEN NO INDICATION THAT THERE WOULD BE A CONFLICT; BUT WE SOON PICKED UP AN ACFT ON TCASII. A FEW MOMENTS LATER; I SAW THE TFC ABOUT 3 MI AWAY AND WE ALSO GOT A TCASII ALERT. THE CAPT COMMENTED THAT WE WERE 1500 FT ABOVE THE TFC AND DSNDING; SO IT MIGHT BE A CONFLICT. CAPT BEGAN TO SHALLOW HER DSCNT AT THAT TIME AND A FEW SECONDS LATER WE GOT AN RA TO REDUCE DSCNT. THE CAPT SHALLOWED THE DSCNT MORE AND HAD THE TFC IN SIGHT. AT ABOUT 7500 FT; CAPT LEVELED OFF AND THE ACFT PASSED ABOVE 1 MI IN FRONT OF US AND 500 FT BELOW US. ABOUT THAT SAME TIME; THE CTLR ADMONISHED US THAT WE WERE SUPPOSED TO BE AT 8000 FT. WE RESPONDED THAT WE HAD BEEN CLRED TO 7000 FT AND HAD READ BACK 7000 FT. HE RESPONDED THAT WE HAD BEEN CLRED TO 8000 FT. AT THAT TIME HE BEGAN TO VECTOR OTHER ACFT AND WE QUERIED HIM ABOUT WHICH ALT HE WANTED US AT. HE CLRED US TO 8000 FT; AND WE CONTINUED TO STL. I THINK THE 2 MAJOR CONTRIBUTING FACTORS ARE THE DIFFICULTY I HAD UNDERSTANDING THE PARTICULAR CTLR; AND THAT CTLRS ARE NOT HELD ACCOUNTABLE TO ENSURE PROPER READBACK. FORTUNATELY; WE HAD THE CONFLICTING TFC INSIGHT VERY EARLY ON AND WERE ABLE TO AVOID SERIOUS HARM.