AN A320 WITH A PRESSURIZATION MEL DID NOT PRESSURIZE AFTER TAKEOFF WHEN MAINTENANCE WAS IMPROPERLY PERFORMED BY MAINTENANCE AT A FOREIGN AIRPORT. AIRCRAFT RETURNED TO LAND.

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ACFT WOULD NOT PRESSURIZE AFTER TKOF. ACFT HAD MEL WHICH REQUIRED A SPECIAL PROCEDURE. THE PROCEDURE WAS ACCOMPLISHED BY CONTRACT MAINT AT ZZZZ AND ENTERED INTO LOGBOOK. ON TKOF ACFT WOULD NOT PRESSURIZE. WE RECEIVED CLRNC TO RETURN TO FIELD AND MADE NORMAL LNDG WITH ACFT BEING BELOW MAX LNDG WT. MEL REQUIRED MAINT TO MANUALLY LOCK CLOSED A VENT VALVE AND IT TURNED OUT THAT AFTER THE PROCEDURE WAS PERFORMED BY THE MECH; ONE OF HIS HELPERS CAME ALONG AND RETURNED THE VALVE TO WHAT HE THOUGHT WAS THE CORRECT POS. ONE OF THE BIG PROBS HERE BESIDES THE MECH NOT BEING FAMILIAR WITH THE AIRBUS WAS THE LANGUAGE BARRIER. THE PROCEDURE WAS ANOTHER TEST; BUT I WAS SATISFIED WITH THE WORK ALTHOUGH I COULD NOT COMMUNICATE VERY WELL WITH THE MECH. THE REASON THAT THE EVENT HAPPENED WAS BECAUSE HIS HELPER DID UNAUTH WORK AND DID IT AFTER THE PROCEDURE WAS ACCOMPLISHED AND SHOWED TO BE OK. THIS EVENT COULD HAVE BEEN AVOIDED IF THE FLT CREW HAD PERFORMED THE PROCEDURE. CONTRACT MAINT IN A FOREIGN COUNTRY ON A PROC LIKE THIS IS ASKING FOR TROUBLE AND THAT IS EXACTLY WHAT WE GOT.