LTSS AT HIGH ALT.

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SCHEDULED FAR 121 ACR ABC SEA-PHX. ACFT AT CRUISE FL330 PROCEEDING DIRECT TO KIMBERLEY VOR AS FILED. I WAS PF ; ACFT ON AUTOPLT. ACFT WEIGHED ABOUT 135000 LBS; THEREFORE FL330 WAS OUR ALT LIMIT. SEATTLE CTR TOLD US TO TURN R 20 DEGS FOR XING TFC. IT WAS ABOUT THIS TIME THAT A FLT ATTENDANT CALLED UP FRONT AND THE CAPT BEGAN SPEAKING ON THE INTERPHONE. WE WERE IN VMC AND SAW ACFT XING L TO R (WBOUND). ATC RPTED THIS ACFT AS DSNDING THROUGH OUR ALT AND DIRECTED US TO TURN L TO 070 DEGS AND EXPEDITE TURN. I USED 25 DEG BANK ANGLE; BECAUSE NEW HDG WAS NEARLY 90 DEGS TO L. MAX TURN AVAILABLE DUE TO OUR WT AND ALT. A BOEING 757 WAS OBSERVED XING L TO R AHEAD OF US AT OUR ALT. WE WERE VMC TURNING AWAY FROM THE 757; PASSING WELL CLR. WE HEARD 1 CALL TO THE OTHER ACFT TO EXPEDITE HIS DSCNT. EVEN THOUGH HE WAS STILL ABOVE US. OUR TCASII GAVE A WARNING AND AN RA; BUT NO VERT MANEUVER WAS TAKEN DUE TO OUR TURNING WELL CLR HORIZ. WE WERE SHORTLY TOLD TO RESUME OUR NAV TO KIMBERLEY VOR. APPROX 10 MINS LATER WE WERE TOLD TO CALL ZSE ON ARR BY PHONE ABOUT A POSSIBLE CONFLICT. IT SEEMS ATC CREATED A CONFLICT BY DSNDING TFC THROUGH OUR ALT WITH INSUFFICIENT HORIZ DISTANCE TO AVOID A CONFLICT. CONTRIBUTING FACTORS MAY HAVE BEEN: 1) COCKPIT DISTRACTED FROM RADIO MOMENTARILY BY FLT ATTENDANT CALL: 2) SIMILAR CALL SIGN ON RADIO SAME ACR ABC; WE MAY HAVE MISSED A CALL: 3) AT CRUISE ON COURSE YOU DO NOT EXPECT TO NEED EVASIVE ACTION; AS YOU MIGHT EXPECT ON DSCNT AND APCH.