E120 CREW HAD ALTDEV.

Narrative

WE WERE OPERATING AS ACR FLT ABCD FROM LAREDO; TX. WE WERE ON A DOWNWIND VECTOR EXPECTING A LNDG ON RWY 27 AT IAH. OUR ALT ASSIGNED WAS 6000 FT. WE WERE TOLD TO CONTACT A SECOND APCH FREQ; BUT WERE UNABLE TO CHK IN DUE TO FREQ CONGESTION. MANY XMISSIONS WERE BEING BLOCKED. AS PLT READ BACK THEIR INSTRUCTIONS; THE CTLR WOULD END UP BLOCKING THEIR READBACKS WITH OTHER ACFT INSTRUCTIONS. WITHOUT BEING ABLE TO CHK-IN BOTH MYSELF AND THE FO HEARD INSTRUCTIONS FOR DIFFERENT ACR ABCD TO DSND AND MAINTAIN 2000 FT. THE FO READ BACK THE CLRNC; BUT WAS BLOCKED BY THE CTLR SAYING TO TURN 360 DEG HDG. THE FO THEN READ BACK DOWN TO 2000 FT AND TURNING 360 DEGS. NOT KNOWING THAT THE READBACK WAS BLOCKED BY THE CTLR OR ANOTHER ACFT; WE COMMENCED THE DSCNT AND TURN. AS WE WERE NBOUND DSNDING THROUGH AROUND 4500 FT; THE CTLR CALLED US AND TOLD US TO TURN R 180 DEGS AND MAINTAIN 4000 FT. I IMMEDIATELY STARTED THE TURN. IN THE TURN THE CTLR TOLD US TO TIGHTEN THE TURN IN WHICH WE DID. AT THIS TIME I ASKED THE CTLR WHAT WAS GOING ON SINCE WE WERE CLRED TO 2000 FT AND HEADING 360 DEGS. HE CAME BACK AND SAID IT WAS FOR A DIFFERENT ACR FLT. AFTER THAT WE WERE VECTORED FOR THE APCH AND LANDED UNEVENTFUL. THE RADIO FREQ BEING VERY CONGESTED AND UNABLE TO READ BACK INSTRUCTIONS WITHOUT BEING BLOCKED BY THE CTLR OR OTHER ACFT WERE THE CONTRIBUTING FACTORS LEADING TO THIS.