A DC9-50 WAS DISPATCHED WITH THE WRONG SVC DOOR DEFERRED. ACFT TOOK OFF AND COULD NOT PRESSURIZE. RETURNED TO FIELD TO CLOSE AN OPEN SVC DOOR.

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AT XA40Z FLT MSP-DFW CONTACTED FLT DISPATCH THAT THEIR FORWARD ACCESSORY COMPARTMENT DOOR LIGHT ANNUNCIATOR HAD STAYED ON; AND THEY WANTED TO DEFER THE LIGHT; THE DOOR WAS CONFIRMED CLOSED BY THE PUSHBACK MECH. ACFT TYPE IS A DC9-50. MAINT CTL DISCUSSED THE PROB WITH THE CREW ON RADIO; WHILE ACFT WAITED TO BE DEICED ON THE RAMP. CREW CONFIRMED AT LEAST TWICE BY VOICE THAT THE PUSHBACK MECH HAD CONFIRMED THE DOOR CLOSED; AND THE LIGHT WAS ON. AS A NON BOXED MEL ITEM; MAINT CTL WENT AHEAD WITH THE DEFERRAL PROCESS WITH THE CREW; AND HAD THE CREW COMPLETE THE PLACARDING PROC FOR MEL DEFERRAL OF DOOR WARNING LIGHT SYS. AFTER CREW AND MAINT HAD DEFERRED THE LIGHT; I AMENDED THE RELEASE AT XB42Z TO ADD THE MEL TO THE CREW'S RELEASE. FLT ACKNOWLEDGED THE AMENDMENT; FINISHED DEICING; AND TOOK OFF AT XC50Z. AT XD55Z CREW CALLED DISPATCH VIA VOICE TO ADVISE THEY WERE UNABLE TO PRESSURIZE THE CABIN. ACFT WAS BELOW MAX LNDG WT; DISPATCH ADVISED CREW TO AMEND RELEASE TO SHOW RETURN TO FIELD; MSP; LANDED WITHOUT INCIDENT. AFTER RETURNING TO THE GATE; CREW DISCOVERED PUSHBACK MECH HAD VERIFIED THE WRONG DOOR CLOSED. THE CAPT HAD ENTERED ON HIS ACFT LOG SHEET THAT THE MECH HAD VERIFIED DOOR CLOSED. THE GATE MAINT DISCOVERED THE PROB; CORRECTED IT; AND CLRED THE MEL BEFORE THE FLT PUSHED; TO RE-DEPART FOR DFW.