C425 ACFT IN CRUISE ON AIRWAY INADVERTENTLY SWITCHED RADIO FREQ. AS THEY APCHED THE NORMAL DSCNT POINT THEY CALLED FOR LOWER ALT AND THE CTLR ON THAT FREQ DIDN'T KNOW ANYTHING ABOUT THEM. AFTER RETURNING TO THE CORRECT FREQ THE CTLR WOULD NOT ANSWER THEIR REPEATED CALLS WHICH MADE FLC THINK THEY HAD LOST THE XMITTER. RPTR BELIEVES THAT THE CTLR WAS IRRITATED WITH THEM BECAUSE HE HAD BEEN UNABLE TO REACH THEM WHEN THEY WERE OFF FREQ AND WAS BEING VENGEFUL.

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WHILE AT 9000 FT MSL; TRACKING SEBOUND ON V459; APPROX 15 NM NW OF SEAL BEACH VORTAC; WE WERE BEING WORKED BY SOCAL APCH CTL ON 124.30. I WAS PROGRAMMING THE COM UNIT TO THE NEXT ANTICIPATED FREQ (121.30). UNKNOWN TO BOTH CREW MEMBERS; THE FREQ 'SWAP' BUTTON MUST HAVE BEEN ACCIDENTALLY DEPRESSED; PROBABLY DUE TO THE FEW BOUNCES WE ENCOUNTERED IN OUR FLT. AS WE APCHED THE POS WHERE WE 'NORMALLY' RECEIVE A LOWER ALT; WE BEGAN TO SUSPECT A COM FAILURE. I CALLED TO ASK FOR A LOWER ALT. THE CTLR WHO RESPONDED INDICATED THAT HE DIDN'T KNOW ANYTHING ABOUT US! HE SUGGESTED WE RETURN TO THE PREVIOUS FREQ. AT THAT POINT; IT WAS REALIZED WE HAD INADVERTENTLY SWITCHED FREQS. WE IMMEDIATELY CHKED-IN ON THE PREVIOUS FREQ. AFTER 4-5 UNANSWERED CALLS TO THIS CTLR; WE NOW SUSPECTED A XMITTER FAILURE. HOWEVER; HE DID FINALLY RESPOND TO US. HE SEEMED VERY IRRITATED. WE GOT THE IMPRESSION THAT WE HAD MISSED NUMEROUS CALLS FROM HIM; BUT WE WERE REALLY ONLY OFF FREQ 2-3 MINS. EVEN AFTER RE-ESTABLISHING CONTACT WITH THE 124.30 CTLR; HE CONTINUED TO IGNORE OUR QUERIES ABOUT OUR RADIOS. HIS REASON FOR IGNORING OUR CALLS? I HAVE NO ANSWER. COULD IT BE THAT HE WAS STILL (SILENTLY) SHOWING HIS IRRITATION? THIS EXPERIENCE EMPHASIZES THE NEED TO BE VIGILANT; EVEN DURING SELECTION OF A STANDBY FREQ. BUT; AFTER DISCOVERY AND CORRECTION OF THIS PROB; THERE WAS NO NEED TO HAVE A CTLR DISPLAY A VENGEFUL ATTITUDE.