ACR MLG OVERSHOT ALT IN CLIMB.

Narrative

LAX CENTER CLRED US TO 26000'. WHEN WE WERE ABOUT 24000' THEY CLRED US DIRECT TO PALMDALE AND UP TO 28000'; PLUS A FREQ CHANGE. THE F/O READ BACK THE CLRNC AND CHANGED FREQ AND CONTACTED THE CENTER ON NEW FREQ AND TOLD THEM WE WERE CLBING TO 28000'. WHEN WE GOT TO 26700' LAX CENTER SAID TO LEVEL AT 26000'. WE TOLD THEM WE WOULD HAVE TO DSND BACK DOWN. THERE WAS A PAUSE AND THEY THEN SAID CLB TO 35000'. SEVERAL MINS WENT BY AND THEY SAID WE HAD ONLY BEEN CLRED TO 26000'. THAT ANOTHER ACFT WAS IN THE AREA AT 28000' AND DSNDING TO 27000'. HOWEVER; HE WASN'T CLOSE TO US. WE DID NOT HAVE TO TAKE ANY EVASIVE ACTION. THE PROB WAS MISCOMS ON ALT CLRED TO. BOTH PARTIES--PLTS AND CTLRS--HAVE TO LISTEN TO READBACKS AND MAKE SURE THAT THEY UNDERSTAND EACH OTHER. ONE PERSON MIGHT BE HEARING WHAT HE WANTS TO HEAR. HE CLRS YOU TO 28000'; WHEN HE MEANT THAT ANOTHER ACFT WAS THERE; OR THAT HE WANTED YOU TO FLY A HDG AT 280 DEGS. WHEN YOU REPEAT IT BACK; HE SAYS ROGER BECAUSE HE HEARD 280; BUT REALLY DIDN'T THINK ABOUT IT AS FAR AS WHAT YOU WERE REALLY SAYING. OR; IT COULD BE THE PLT DOING THE SAME THING--HEARING WHAT HE WANTS TO HEAR. BOTH SIDES HAVE TO PAY CLOSE ATTN TO WHAT IS BEING SAID AND NOT TAKE IT AS ROUTINE COMS.