A737-300 CREW LEVELED AT A LOWER ALT THAN CUSTOMARY; AND BELOW MSA DEPARTING DFW.

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I BELIEVE THIS IS AN EXAMPLE OF A COM FAILURE. MY FO RECEIVED THE DEP CLRNC AND GAVE A FULL READBACK TO CLRNC DELIVERY STATING 2000 FT AS OUR CLRNC ALT. HE FILLED OUT OUR TKOF CARD WITH 2000 FT NOTED ON OUR ALT BOX. I BELIEVE THE CORRECT ALT SHOULD HAVE BEEN 10000 FT. I BRIEFED OUR DEP OFF THE 'TOLD' CARD AND STATED THE ALT OF 2000 FT MSL AS OUR ALT CLRNC LIMIT. I MENTALLY NOTED THAT THIS WAS PROBABLY DUE TO XING TFC. AFTER OUR TKOF; PASSING APPROX 800 FT MSL; THE FO CHKED IN WITH DEP CTL AND STATED WE WERE CLBING TO 2000 FT. DEP ACKNOWLEDGED; AND I PROCEEDED TO LEVEL OFF AT 2000 FT. WE CONTINUED ON OUR 185 DEG ASSIGNED HDG FOR ABOUT 1 MIN BEFORE ATC ASKED US OUR ASSIGNED ALT. WE RPTED 2000 FT AND HE IMMEDIATELY CLRED US TO 10000 FT. I BELIEVE THAT THERE WAS A FAILURE IN THE COM SAFETY NET HERE; BOTH ON THE ATC SIDE (CLRNC DELIVERY AND DEP CTL) AND MYSELF NOT CHKING BEFORE TKOF THE MSA WHICH OUR CHART SHOWS AT 3500 FT. DURING OUR LEVELOFF AT 2000 FT; BOTH THE FO AND MYSELF COMMENTED ON THIS BEING SUCH A LOW ALT. I SHOULD HAVE QUERIED ATC. I WILL IN THE FUTURE. WE WERE IN AND OUT OF A CLOUD DECK (BROKEN LAYER) AND FARTHER S OF OUR RTE WERE SOME TWRS ON OUR CHART AT 2349 FT MSL WE FOUND OUT LATER. I BELIEVE MORE VIGILANCE NEEDS TO BE EXERCISED ON LISTENING TO READBACK CLRNCS BOTH BY ATC AND THE PLT COMMUNITIES. ALSO; I NEED TO QUESTION ATC WHEN A CLRNC SEEMS UNUSUAL. SUPPLEMENTAL INFO FROM ACN 513992: DFW TO PHX APPROX XB10 RECEIVED CLRNC 'CLRED PHX NORTH3.ABI TRANSITION 2000 FT; SQUAWK XXXX.' I READ BACK CLRNC VERBATIM WITH AN ALT OF 2000 FT. CLRNC STATED 'READBACK CORRECT.' APPROX XB42 WE RECEIVED CLRNC FROM TWR FOR TKOF AND ASSIGNED HDG 185 DEGS. AFTER WE WERE HANDED OFF TO DEP I CHKED IN CALLING 'FORT WORTH DEP; 1400 FT FOR 2000 FT.' THE CTLR RESPONDED RADAR CONTACT. WE LEVELED OFF AT 2000 FT. AFTER BEING LEVEL FOR ABOUT 30 SECONDS; I MADE A COMMENT TO THE CAPT ABOUT A B737 SHOULDN'T BE FLYING AT 1500 FT AGL. HE AGREED. APPROX 10 SECONDS AFTER MY COMMENT; FORT WORTH APCH ASKED WHAT OUR ASSIGNED ALT WAS. I TOLD HIM 2000 FT. AFTER A BRIEF PAUSE THE CTLR SAID 'CLB TO 10000 FT;' THEN LATER 17000 FT. NOTHING ELSE WAS STATED OTHER THAN ANOTHER HDG TO JOIN THE DEP AND CONTACT ZFW.