KING AIR B200 PLT HAS LOST COM WHILE ENRTE MMLP TO KCXL.

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I WAS RETURNING TO THE UNITED STATES VIA UJ9 FROM MMLP (LA PAZ) TO KCXL (CALEXICO) AT FL240. THERE WAS A THIN OVCST LAYER AT FL250 AND SCATTERED TSTM IN SOCAL AND NORTHERN BAJA. ABOUT 45 MINS PRIOR TO OUR ARR IN THE UNITED STATES; I LOST COMS WITH MAZATLAN CTR. I TRIED ALL 3 FREQS FOR THEM WITH NO RESPONSE. I DID NOT HEAR ANY OTHER ACFT EITHER. I ATTEMPTED MAZATLAN ON 121.5 WITH NO REPLY. AT THAT TIME I ENTERED 7600 IN MY XPONDER. I ALSO HAD TO START DOWN TO MAINTAIN VMC AND TO MAKE KCXL AT THE PROPER TIME. I RPTED THIS IN THE 'BLIND' ON 121.5. AT THAT TIME AN AIRLINER CALLED ME AND ASKED IF THEY COULD RELAY A MESSAGE TO MAZATLAN. I SAID YES AND STARTED TO GIVE HIM THE INFO. THEN ZLA CALLED AND SAID THAT THEY WERE ALREADY TALKING WITH MAZATLAN AND GAVE ME A NEW FREQ TO TRY. I REACHED MAZATLAN AS I PASSED THROUGH FL270 (APPROX). THE CTLR WAS VERY ANGRY AND ASKED ME WHO APPROVED MY DSCNT. TOLD HIM THAT I COULDN'T REACH ANYONE AND THAT I HAD TO START DOWN FOR KCXL AND TO REMAIN VMC FOR LOST COM. HE CLRED ME DOWN TO 10000 FT (I THINK) AND TOLD ME TO CONTACT MEXICALI APCH CTL; WHICH I DID. MEXICALI SAID THAT THEY HAD A MESSAGE FROM MAZATLAN THAT THEY HAD A PHONE NUMBER THEY WANT ME TO CALL ONCE ON THE GND. I WAS INSTRUCTED TO ASK FOR A SUPVR. AFTER CLRING CUSTOMS IN KCXL; I CALLED SEVERAL TIMES AND GOT ONLY A BUSY SIGNAL. I FLEW HOME TO KCMA (CAMARILLO) 45 MINS AND CALLED AGAIN SEVERAL TIMES. I FINALLY GOT THROUGH; WAS XFERRED TO SOMEONE WHO SPOKE ENGLISH; BUT WAS NOT A SUPVR. HE SAID HE WOULD GIVE MY NAME AND TAIL NUMBER TO THE SUPVR WHEN HE RETURNED.