A B757 FREIGHTER CREW EXPERIENCES A REPLY TO WRONG CALL SIGN AND ACCEPTS AN UNAUTH UNCOORD CLB FROM ZDV BEFORE A HDOF IS EFFECTED FROM DEN DEP CTLR.

Narrative

WE WERE ON DEP WITH DEN DEP CTL. WE HAD BEEN GIVEN A HDG; AN INTERCEPT; AND AN ALT. WHILE ACCOMPLISHING THIS; WE HEARD PART OF A BLOCKED XMISSION FROM DEN DEP 'XXX ABC CONTACT ZDV ON XXX.XX.' THE CAPT RESPONDED (OUR CALL SIGN WAS XXXFABC) WITHOUT OUR CALL SIGN AND SWITCHED FREQS. ZDV THEN GAVE US A CLB TO FL290. AFTER WE COMPLETED THE INTERCEPT HDG; I NOTICED THE ALT SELECTOR AT 16200 FT. I ASKED WHAT ALT WE WERE GOING TO AND THE CAPT CONFIRMED WITH CTR WHO SAID; 'NOW CLB TO FL330 BUT PREVIOUS WAS FL290.' THEN HE SENT US BACK TO DEN DEP CTL WHO ASKED US WHO GAVE US PERMISSION TO CLB BECAUSE WE VIOLATED ANOTHER ACFT'S AIRSPACE. SPACE NEEDED WAS 5 MI; WE PASSED WITHIN 4.1 MI. WE CALLED CTR WHEN ON THE GND AND THEY EXPLAINED THAT WE TOOK ANOTHER ACFT'S INSTRUCTION TO CHANGE FREQS; BUT THAT ZDV DID ISSUE A CLB CLRNC TO US WHEN HE HAD NOT YET ACCEPTED A HDOF OF US FROM DEP CTL. WE SHOULD BE MORE DILIGENT WITH OUR CALL SIGN IN THE FUTURE AND THEY WOULD TALK TO ZDV ABOUT THEIR ROLE. NO FURTHER ACTION WILL BE TAKEN CONCERNING US.