both customers said they said they tested it on several jacks
Maybe its your phone that is reversed? I recommend you buy a cheap $5 - $10 line polarity tester with red and green leds that you can use at your home. That way you will have a benchmark to work from.
I also recommend that you make a test jig to test all your phones. That way, the polarity sensitive ones can be listed in your description. Let it be a selling tool and describe them as OEM wired!
