B757 DEP FROM MDE EXPERIENCED TFC CONFLICT AT APPROX FL240.

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INITIAL CLRNC ON GND IN SKRG WAS TO CLB TO FL350. ON CLBOUT; SKRG DEP CTLR SAID TO RPT CLBING THROUGH FL240 AND CLB TO FL350. AT ABOUT FL230; SKED INSTRUCTED US TO CLB TO FL250. WE ASKED TO CLARIFY FL250 OR FL350 AND THEY CONFIRMED FL250 AND WE READ BACK FL250. WE LEVELED AT FL250. SHORTLY AFTER SKED INSTRUCTED TO DSND TO FL240 FOR TFC. WE CLARIFIED AGAIN FL240 AND CONFIRMED FL240. I INITIATED A DSCNT OF 1500 FPM TO FL240 AND WE SAW ON TCASII ANOTHER ACFT AT 12 O'CLOCK POS AND 8 MI THAT WAS SHOWING 100 FT LOWER THAN US AT FL250. WE GOT THE 'TFC; TFC' WARNING AND FOLLOWED BY THE 'ADJUST VERT SPD' WARNING. WE NEVER SAW THE ACFT. TCASII WAS IN THE RA MODE NOW SHOWING A GREEN BAND BTWN ZERO AND 300 FPM DOWN THE TFC WAS ALSO DSNDING FOR SOME REASON AND ATC WAS TALKING IN SPANISH TO THEM. I LEVELED OFF AT FL243 AS OTHER ACFT WENT UNDER US AT ABOUT FL235. ATC THEN GAVE US CLRNC TO CLB TO FL350 AND CHANGE TO BOG CTL. THOUGHT THIS ORDER VERY DIFFICULT TO UNDERSTAND AND THE CTLR'S ENGLISH WAS MARGINAL. WE CONFIRMED EACH ASSIGNMENT WITH THE ATC FACILITY AND WITH EACH OTHER BEFORE EXECUTING AND BELIEVE WE WERE FOLLOWING THE INSTRUCTIONS AS SAID. A CONVERSATION OF A FEW MINS CONTINUED IN SPANISH BTWN ATC AND THE OTHER ACFT.