SF340 CAPTAIN REPORTS CALL SIGN ERRORS MADE BY THE FIRST OFFICER AND THE TOWER RESULTING IN THE ACFT DEPARTING FROM THE WRONG RWY USING THE WRONG CALL SIGN.

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THE FO HAD OBTAINED OUR PROPER CLRNC FOR OUR FLT. ON THE TAXI OUT; THE FO CALLED FOR TAXI AND USED THE WRONG FLT NUMBER. I; AS THE CAPT DID NOT NOTICE THE INCORRECT FLT NUMBER. WE WERE GIVEN CLRNC TO TAXI TO THE RWY VIA TXWY N. WE BOTH THOUGHT THIS WAS STRANGE AS THIS IS NOT THE STANDARD RWY FOR OUR DIRECTION OF DEP. HOWEVER; NEITHER OF US QUESTIONED THE CLRNC. TWR CLRED US INTO POS AND HOLD AT THE RWY BUT CALLED US FLT Y AND THE FO CORRECTED THE CTLR AND IT SEEMED HE MADE A MISTAKE AS HE DID NOT QUESTION THE CORRECTION MADE BY THE FO. WE WERE CLRED FOR TKOF AND TWR CALLED US FLT Y AGAIN AND THE FO CORRECTED HIM AGAIN THAT WE WERE FLT X (AGAIN THE FO STATED THE WRONG FLT NUMBER FOR US; BUT THE STATIC OVER THE INTERCOM PREVENTED ME FROM HEARING THE FO CALLING US THE WRONG FLT NUMBER). ONCE AIRBORNE; THE TWR CTLR NOTICED SOMETHING WAS WRONG AND ASKED US OUR DEST. DEP CTL GAVE US A PHONE NUMBER TO CALL ONCE ON THE GND. I TALKED TO THE SUPVR AT DEP CTL ABOUT THE SITUATION. WE DISCOVERED 2 ERRORS. THE FO USED THE WRONG FLT NUMBER ON THE INITIAL CALL; WHICH EXPLAINED THE WRONG RWY FOR THE DEP; AND THE TWR CTLR PULLED THE WRONG STRIP WHEN CLRING US FOR TKOF. I THINK THIS SITUATION HAPPENED DUE TO SEVERAL FACTORS. ONE BEING THAT I AS THE CAPT DID NOT QUESTION OUR TAXI CLRNC TO DEPART OFF THE NON-STANDARD RWY. SECOND; THE SAAB INTERCOM HAS INHERENTLY A LOT OF BACKGROUND NOISE WHICH DID NOT ALLOW ME TO HEAR THE DIFFERENCE BTWN FLT X AND FLT Y. THIRD; THE FO MISREAD THE FLT NUMBER FROM THE RELEASE. EVERYONE NEEDS TO LISTEN CAREFULLY TO EACH OTHER ON THE RADIO. EVERYONE MISSED SEVERAL OPPORTUNITIES TO CATCH THE MISTAKE. ALSO; WE NEED TO IMPLEMENT A SYS THAT ALLOWS THE PLTS TO RPT TO THE COMPANY SIMILAR SOUNDING FLT NUMBERS THAT LEAD TO CONFUSION. DURING THIS TIME OF THE MORNING; THERE WERE 3 FLTS ALL TAXIING AT THE SAME TIME.