PLT OF C560XL ON VFR DEP FROM UNCTLED GKY CLBED INTO DFW CLASS B PRIOR TO OBTAINING IFR CLRNC.

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OUR PLAN ON DEP FROM UNCTLED GKY BELOW THE DALLAS/FT WORTH CLASS B AIRSPACE WAS TO PICK UP OUR IFR CLRNC WHEN AIRBORNE FROM DALLAS DEP. WE TOOK OFF AND WHILE EXPEDITING OUR CLB THROUGH 2500 FT FOR THE OBSTACLE DEP PROC; CONTACTED DEP REQUESTING CLRNC TO OUR DEST. I EXPECTED A SQUAWK CODE AND CLB. INSTEAD WE WERE ASKED WHY WE DIDN'T HAVE OUR IFR CLRNC ALREADY AND TOLD TO 'HOLD' SW OF ARLINGTON. ATC THEN REFED A 'NOTE' ABOUT REQUESTING IFR CLRNCS ON THE GND AT GKY. WE RESPONDED WE WERE FIRST-TIMERS AT GKY AND HAD SEEN NO 'NOTE' (OR NOTAM) REGARDING THIS. DURING THE CONFUSION SORTING ALL THIS OUT I LEVELED THE ACFT AT 3000 FT MSL MOMENTARILY BEFORE STARTING BACK DOWN TO 2500 FT TO REMAIN CLR OF CLASS B. THE CTLR STATED WE WERE IN CLASS B AIRSPACE. AFTER A FEW MINS WE WERE CLRED IFR TO OUR DEST AND DEPARTED. WE COULD HAVE PICKED UP OUR IFR ON GND WITH REGIONAL CLRNC. WE FREQUENTLY OPERATE OUT OF UNCTLED ARPTS AND ARE USED TO PICKING UP CLRNCS ON DEP. WE SELDOM OPERATE OUT OF UNCTLED FIELDS UNDER A TCA (CLASS B). WE EXPECTED A LOT MORE ASSISTANCE FROM DEP THAN WE RECEIVED. WHILE I HAD REVIEWED THE CLASS B PLATE AND HAD IT ON MY YOKE I SHOULD HAVE REMAINED BELOW 3000 FT UNTIL CLRED INTO TCA (CLASS B).